Tracing precedents in external spreadsheets using Excel VBA - excel

Question

I'm currently trying to trace the dependencies of a complex set of Excel spreadsheets. My ideal end goal would be a tree structure, starting with my first spreadsheet. However, I don't want to include all of the dependencies of the child spreadsheets, just the ones of the cells referenced by the original spreadsheet. For example:
In cell A1 of my first workbook:
somebook.xls!Sheet1!C2
I want to look at cell C2 in sheet 1 of somebook.xls for its (external) dependencies, and then recurse.
At the moment I'm using LinkInfo to get a list of external dependencies, searching using Find, and I'm struggling with vbscript's primitive regex capabilities to try and extract the address out of the cells I find. This is not a brilliant way of doing things.
Does anyone know if Excel will tell you which cells in an external spreadsheet are being referenced? If not, any other tools that might help?
Thanks.

Answer 1

This answer is based off Bill Manville's macro from many years back. The macro still works, but I broke it out into functions allowing for more flexibility and reusability. The main addition by me is the ability to find external dependencies only, and the extension to both precedents and dependents. I also added a call to a custom macro called unhideAll; this was necessary for me as dependencies were not being found in hidden worksheets.
'Module for examining depedencies to/from a sheet from/to other sheets
Option Explicit
Sub showExternalDependents()
Dim deps As Collection
Set deps = findExternalDependents(ActiveCell)
Call showDents(deps, True, "External Dependents: ")
End Sub
Sub showExternalPrecedents()
Dim precs As Collection
Set precs = findExternalPrecedents(ActiveCell)
Call showDents(precs, True, "External Precedents: ")
End Sub
'external determines whether or not to print out the absolute address including workbook & worksheet
Sub showDents(dents As Collection, external As Boolean, header As String)
Dim dent As Variant
Dim stMsg As String
stMsg = ""
For Each dent In dents
stMsg = stMsg & vbNewLine & dent.Address(external:=external)
Next dent
MsgBox header & stMsg
End Sub
Function findPrecedents(rng As Range) As Collection
Set findPrecedents = findDents(rng, True)
End Function
Function findDependents(rng As Range) As Collection
Set findDependents = findDents(rng, False)
End Function
Function findExternalPrecedents(rng As Range) As Collection
Set findExternalPrecedents = findExternalDents(rng, True)
End Function
Function findExternalDependents(rng As Range) As Collection
Set findExternalDependents = findExternalDents(rng, False)
End Function
'Gives back only the dependencies that are not on the same sheet as rng
Function findExternalDents(rng As Range, precDir As Boolean) As Collection
Dim dents As New Collection
Dim dent As Range
Dim d As Variant
Dim ws As Worksheet
Set ws = rng.Worksheet
For Each d In findDents(rng, precDir)
Set dent = d
With dent
If Not (.Worksheet.Name = ws.Name And .Worksheet.Parent.Name = ws.Parent.Name) Then _
dents.Add Item:=dent
End With
Next d
Set findExternalDents = dents
End Function
'this procedure finds the cells which are the direct precedents/dependents of the active cell
'If precDir is true, then we look for precedents, else we look for dependents
Function findDents(rng As Range, precDir As Boolean) As Collection
'Need to unhide sheets for external dependencies or the navigate arrow won't work
Call mUnhideAll
Dim rLast As Range, iLinkNum As Integer, iArrowNum As Integer
Dim dents As New Collection
Dim bNewArrow As Boolean
'Appliciation.ScreenUpdating = False
If precDir Then
ActiveCell.showPrecedents
Else
ActiveCell.ShowDependents
End If
Set rLast = rng
iArrowNum = 1
iLinkNum = 1
bNewArrow = True
Do
Do
Application.Goto rLast
On Error Resume Next
ActiveCell.NavigateArrow TowardPrecedent:=precDir, ArrowNumber:=iArrowNum, LinkNumber:=iLinkNum
If Err.Number > 0 Then Exit Do
On Error GoTo 0
If rLast.Address(external:=True) = ActiveCell.Address(external:=True) Then Exit Do
bNewArrow = False
dents.Add Item:=Selection
iLinkNum = iLinkNum + 1 ' try another link
Loop
If bNewArrow Then Exit Do
iLinkNum = 1
bNewArrow = True
iArrowNum = iArrowNum + 1 'try another arrow
Loop
rLast.Parent.ClearArrows
Application.Goto rLast
Set findDents = dents
End Function
Sub mUnhideAll()
'
' mUnhideAll Macro
'
' Unhide All
Dim ws As Worksheet
For Each ws In Worksheets
ws.Visible = True
Next
'Sheets("Sprint Schedule Worksheet").Visible = False
End Sub

Answer 2

Excel's built in support, as you're finding, is limited and can be extremely frustrating.
In my experience, I've found a couple of tools from http://www.aivosto.com/ to be useful; Visustin v6 is especially useful for code related auditting/processing.

Answer 3

Here's a simpler version of Colm Bhandal's findDents and findExternalDents. It assumes all worksheets were made visible and arrows were cleared before use.
Function findDents(rCell As Range, bPrec As Boolean) As Collection
'Return all direct precedents (bPrec=True) or dependents (bPrec=False) of rCell
Dim sAddr As String, nLink As Integer, nArrow As Integer
Const bAbs As Boolean = False, bExt As Boolean = True
Set findDents = New Collection
If bPrec Then
rCell.showPrecedents ' even if rCell has no formula
Else
rCell.showDependents
End If
On Error Resume Next ' ignore errors
sAddr = rCell.Address(bAbs, bAbs, xlA1, bExt)
nArrow = 1
Do
nLink = 1
Do
rCell.NavigateArrow bPrec, nArrow, nLink
If ActiveCell.Address(bAbs, bAbs, xlA1, bExt) = sAddr Then Exit Do
findDents.Add Selection ' possibly more than one cell
nLink = nLink + 1
Loop
If nLink = 1 Then Exit Do
nArrow = nArrow + 1
Loop
On Error GoTo 0
If bPrec Then
rCell.showPrecedents Remove:=True
Else
rCell.showDependents Remove:=True
End If
End Function
Function findExternalDents(rCell As Range, bPrec As Boolean) As Collection
'Return ...Dents that are NOT in the same workbook and worksheet as rCell
Dim rDent As Range, wsName As String, wbName As String
With rCell.Worksheet: wsName = .Name: wbName = .Parent.Name: End With
Set findExternalDents = New Collection
For Each rDent In findDents(rCell, bPrec)
If rDent.Worksheet.Name <> wsName Or rDent.Worksheet.Parent.Name <> wbName Then findExternalDents.Add Item:=rDent
Next rDent
End Function
You might want to modify this to use a SortedList instead of a Collection. In that case, change
findDents.Add Selection
to
findDents.Add Selection.Address(bAbs, bAbs, xlA1, bExt), Null