Fill a cell with VBA if contents get deleted by User - excel

Question

I am designing a time report for my colleagues. There are cells which contain a (hidden) formula but are unprotected because I need the user to still be able to manually override the formula.
Now, if a user enters his/her own content and then deletes it again, the cell is empty, which is what I don't want, as it will only lead to confusion.
I want to write a VBA macro which recognizes if the cell contents in a previously declared range are deleted / empty and if they are deleted / empty, then a formula from another (password-protected and hidden) cell should be copied to the empty cell.
Private Sub Worksheet_Change(ByVal Target As Range)
Dim myRange As Range
Set myRange = Intersect(Range("F9:I108"), Target)
If Not myRange Is Nothing Then
'I'm guessing something with WorksheetFunction and possibly CountA,
'but I don't know how to make it work
End If
End Sub
The formulas which should be entered if the content of a cell (or of multiple cells) is deleted is always in line 117 (same worksheet). For example, if the user deletes G50, then G117's formula should be copied into G50 in the same way you usually copy formulas in Excel (so if there's a non-$-reference in G117 that points to A117, it should then point to A50 after the formula is copied to G50).
If possible, I want to work without loops--they always take so long to execute.
Thanks in advance!

Answer 1

Here is a super simple example that involves only 3 cells, A1, A2 and A3. You must modify this to accommodate your formula-cells.
We first create a secret worksheet (called secret). We place the formulas from A1 through A3 from the main worksheet into the secret sheet, but we store them as Strings rather than Formulas:
Then we put the following worksheet event macro in the main sheet:
Private Sub Worksheet_Change(ByVal Target As Range)
Dim rng As Range
Set rng = Range("A1:A3")
If Intersect(Target, rng) Is Nothing Then Exit Sub
If Target.Count <> 1 Then Exit Sub
If Target.Value <> "" Then Exit Sub
Application.EnableEvents = False
Target.Formula = Sheets("secret").Range(Target.Address).Value
Application.EnableEvents = True
End Sub
The sub monitors changes to the three cells and if any of them are cleared, that formula will be restored from the secret worksheet.
Because it is worksheet code, it is very easy to install and automatic to use:
right-click the tab name near the bottom of the Excel window
select View Code - this brings up a VBE window
paste the stuff in and close the VBE window
If you have any concerns, first try it on a trial worksheet.
If you save the workbook, the macro will be saved with it.
If you are using a version of Excel later then 2003, you must save
the file as .xlsm rather than .xlsx
To remove the macro:
bring up the VBE windows as above
clear the code out
close the VBE window
To learn more about macros in general, see:
http://www.mvps.org/dmcritchie/excel/getstarted.htm
and
http://msdn.microsoft.com/en-us/library/ee814735(v=office.14).aspx
To learn more about Event Macros (worksheet code), see:
http://www.mvps.org/dmcritchie/excel/event.htm
Macros must be enabled for this to work!

Answer 2

Here's another possible answer. In order to copy the formula and have it maintain the "relative addressing" of the formula, you need to copy using the R1C1 notation. So a quick sub for this could look like
Option Explicit
Sub RestoreFormula(ByRef emptyCell As Range)
Dim formulaWS As Worksheet
Dim formulaCell As Range
Set formulaWS = ThisWorkbook.Sheets("Sheet1")
Set formulaCell = formulaWS.Range("A17")
emptyCell.FormulaR1C1 = formulaCell.FormulaR1C1
End Sub
The important line here is the emptyCell.FormulaR1C1 = formulaCell.FormulaR1C1 part.
Then, over in the Worksheet_Change event it could look like this
Option Explicit
Private Sub Worksheet_Change(ByVal Target As Range)
Dim checkRange As Range
Set checkRange = ActiveSheet.Range("A1:A9")
If Not Intersect(checkRange, Target) Is Nothing Then
Dim changedCell As Range
For Each changedCell In Target
If IsEmpty(changedCell) Then
RestoreFormula changedCell
End If
Next changedCell
End If
End Sub

Answer 3

If anyone else ever has the same problem and maybe wants to use my solution, which is a combination of PeterT's and Gary's Student's suggestions (thank you both so much):
First I created a new worksheet, in which I copied all of the formulas I wish to retain. I made sure to copy them to the exact same cell as in the original sheet.
Then I appended this code to the original worksheet:
Option Explicit
Private Sub Worksheet_Change(ByVal Target As Range)
Dim Bereich1 As Range
Set Bereich1 = Range("F9:I108") 'Do NOT enter multiple, non-contiguous ranges here! It crashes Excel!
If Not Intersect(Bereich1, Target) Is Nothing Then
Dim changedCell1 As Range
For Each changedCell1 In Target
If changedCell1 = "" Then
changedCell1.Formula = Sheets("Tagebuch_secret").Range(changedCell1.Address).Formula
End If
Next changedCell1
End If
Dim Bereich2 As Range
Set Bereich2 = Range("E112") 'instead duplicate the code snippet
If Not Intersect(Bereich2, Target) Is Nothing Then
Dim changedCell2 As Range
For Each changedCell2 In Target
If changedCell2 = "" Then
changedCell2.Formula = Sheets("Tagebuch_secret").Range(changedCell2.Address).Formula
End If
Next changedCell2
End If
End Sub
This works fine for every scenario in which cell contents get deleted, both if the user deletes contents of a single or multiple cells!
My next step is to make the _secret sheet very hidden, password-protect the workbook structure and then password-protect my vba project. Then only people who know the password (me) can destroy my file :)