Code seems to run forever and Error: block variable not set (VBA) - excel

Question

I am completely new to VBA so please bear with me.
I am trying to write a sub-procedure that will loop through each row in a certain column and compare to another sheet's criteria. if it contains "x", for example, then the value will be returned. However, when I try running the code, the codes run forever and causes the computer to hang.
Here's the code that I have written so far. It keeps prompting an error: Object variable and with block variable not set. PS: I have obtained errors when using 'Application.WorksheetFunction.Index' and when reading other threads, it was suggested to delete 'WorksheetFunction'. I'm not sure if that causes the problem and I would also like to clarify the rationale behind removing the words 'WorksheetFunction'
Thank you so much in advance!
Sub sub_inputData()
Dim ws As Worksheet: Set ws = ActiveSheet
Dim lastrow as range
lastrow = ws.Cells (ws.Rows.Count, 17).End (xlUp).row
Dim rng As Range
Set rng = ws.Range("Q4:Q" & lastrow)
Dim rngCell As Range
On Error Resume Next
For Each rngCell In rng
If rngCell.Offset(0, -13) = "x" Then
rngCell = Application.Index(Sheets("Data").Range _
("D805:D813"), Application.Match(rngCell.Offset(0, -15), Sheets("Data").Range _
("D805:D813"), 1))
ElseIf rngCell.Offset(0, -13) = "y" Then
rngCell = Application.Index(Sheets("Data").Range _
("D27:D34"), Application.Match(rngCell.Offset(0, -15), Sheets("Data").Range _
("D27:D34"), 1))
ElseIf rngCell.Offset(0, -13) = "z" Then
rngCell = Application.Index(Sheets("Data").Range _
("D718:D726"), Application.Match(rngCell.Offset(0, -15), Sheets("Data").Range _
("D718:D726"), 1))
Else: rngCell = vbNullString
End If
Next rngCell
Call sub_code2
Call sub_code3
Set rngCell = Nothing
Set rng = Nothing
End Sub

Answer 1

Couple issue with your code that has been modified here.
1) Dim lastrow As Long, not Range
2) Else: is not necessary, just use Else
3) Set rngCell = Nothing & Set rng = Nothing is not necessary. See this link for explanation
4) Since you are only checking the value of 1 cell, you can use Select Case for a moderately cleaner code.
5) On Error Resume Next is no good for de-bugging code. You want to see the errors so you can handle them. I recommend looking up the do's and dont's of that bit of code.
Sub sub_inputData()
Dim ws As Worksheet: Set ws = ActiveSheet
Dim lastrow As Long: lastrow = ws.Range("Q" & ws.Rows.Count).End(xlUp).Row
Dim rng As Range: Set rng = ws.Range("Q4:Q" & lastrow)
Dim rngCell As Range
Application.ScreenUpdating = False
Application.Calculation = xlCalculationManual
For Each rngCell In rng
Select Case rngCell.Offset(0, -13)
Case "x"
rngCell = Application.Index(Sheets("Data").Range _
("D805:D813"), Application.Match(rngCell.Offset(0, -15), Sheets("Data").Range _
("D805:D813"), 1))
Case "y"
rngCell = Application.Index(Sheets("Data").Range _
("D27:D34"), Application.Match(rngCell.Offset(0, -15), Sheets("Data").Range _
("D27:D34"), 1))
Case "z"
rngCell = Application.Index(Sheets("Data").Range _
("D718:D726"), Application.Match(rngCell.Offset(0, -15), Sheets("Data").Range _
("D718:D726"), 1))
Case Else
rngCell = ""
End Select
Next rngCell
Application.ScreenUpdating = True
Application.Calculation = xlCalculationAutomatic
Call sub_code2
Call sub_code3
End Sub

Answer 2

another possibility is using Switch() function:
Sub sub_inputData()
Dim rngCell As Range, rangeToSearch As Range
Dim val As Variant
With ActiveSheet ' reference data sheet (better: With Worksheets("MyDataSheetName"))
For Each rngCell In .Range("Q4", .Cells(.Rows.Count, "Q").End(xlUp)) ' loop throughreferenced sheet column Q cells from row 4 down to last not empty one
val = rngCell.Offset(, -13).Value2 ' store column D current cell row value
Set rangeToSearch = Sheets("Data").Range(Switch(val = "x", "D805:D813", val = "y", "D27:D34", val = "z", "D718:D726", True, "A1")) ' set range to search into with respect to stored value. set it to "A1" to signal no search is needed
If rangeToSearch.Address <> "$A$1" Then ' if search is needed
rngCell.Value = Application.Index(rangeToSearch, Application.Match(rngCell.Offset(, -15).Value2, rangeToSearch, 1)) 'do the lookup
Else
rngCell.ClearContents ' clear current cell
End If
Next
End With
sub_code2 ' no need for 'Call' keyword
sub_code3 ' no need for 'Call' keyword
End Sub

Answer 3

It looks like you are effectively picking a lookup range based on the value in column D, and then doing a lookup against that range based on the value in column B.
If so, you can do this entirely with formulas, which will be more efficient because it will only run on particular cells when needed (i.e. only when their inputs change).
Here's an example, using Tables and Table Notation. Tables are perfect for this, as you never have to amend your formulas to handle new data.
The formula in C2 is =VLOOKUP([#ID],CHOOSE(VLOOKUP([#Condition],Conditions,2,FALSE),X,Y,Z),2,FALSE)
That formula uses the 'Conditions' Table in E1:F3 to work out which of the other tables to do the lookup on. I've named those other tables X, Y, and Z.