How do I change my macro into a Worksheet_Change event Excel VBA - vba

Question

I have a macro that I call when the workbook closes. It checks the columns in two tables on separate worksheets and assigns row numbers based on what it finds.
Worksheet_Change handler is located on the sheet with Projects range. Database range is located on another worksheet in the same workbook.
Whenever I call the macro anywhere else, it either generates an error or causes an usual bug where excel is partially frozen (anyone know what the hell this is?!?!?!).
Anyway, my last resort before giving up is to change the macro into a worksheet change event and I was wondering if I could get some help creating this.
The original macro:
Sub FindRow()
'This module verifies row numbers in the database by matching them to the opportunities in the Projects
'worksheet. It then assigns row numbers in the Projects worksheet.
Application.ScreenUpdating = False
Dim LastRow As Long
LastRow = Application.ThisWorkbook.Sheets("Projects").Cells.Find("*", SearchOrder:=xlByRows, SearchDirection:=xlPrevious).Row
Dim rng As Range
Dim foundRng As Range
For Each rng In Sheets("Projects").Range("B2:B" & LastRow)
Set foundRng = Sheets("Database").Range("C:C").Find(rng, LookIn:=xlValues, lookat:=xlWhole)
If Not foundRng Is Nothing Then
rng.Offset(0, -1) = foundRng.Row
End If
Next rng
Application.ScreenUpdating = True
End Sub
My proposed change:
Public Sub Worksheet_Change(ByVal Target As Range)
Dim Records As Range
Set Records = Range("Records")
If Not Application.Intersect(Records, Range(Target.Address)) Is Nothing Then
Application.ScreenUpdating = False
Dim LastRow As Long
LastRow = Application.ThisWorkbook.Sheets("Projects").Cells.Find("*", SearchOrder:=xlByRows, SearchDirection:=xlPrevious).Row
Dim rng As Range
Dim foundRng As Range
For Each rng In Sheets("Projects").Range("B2:B" & LastRow)
Set foundRng = Sheets("Database").Range("C:C").Find(rng, LookIn:=xlValues, lookat:=xlWhole)
If Not foundRng Is Nothing Then
rng.Offset(0, -1) = foundRng.Row
End If
Next rng
Application.ScreenUpdating = True
End If
End Sub
However, I keep getting an error on the line that defines the variable LastRow.
I get an application-defined error even though everything is defined properly before.
Thanks in advance.

Answer 1

Worksheet_Change handles is located on the sheet with Projects range. Database range is located on another worksheet in the same workbook. – Remi 1 min ago
This means rng is also on the Projects sheet:
For Each rng In Sheets("Projects").Range("B2:B" & LastRow)
(BTW Me.Range("B2:B" & LastRow) would have been much less ambiguous here)
You're handling a Worksheet_Change event on the Projects sheet, which Excel fires whenever a cell value changes on the Projects sheet. Then inside that handler, you do this:
rng.Offset(0, -1) = foundRng.Row
With rng being a range on the Projects sheet, you're entering a recursive cycle of sheet changes, and that is likely what's crashing your code.
When you make worksheet changes while handling worksheet changes, you need to tell Excel "it's okay, I got this", by preventing it from re-firing the Worksheet.Change event every time:
Application.EnableEvents = False
'...code...
Application.EnableEvents = True
Moreover, when you toggle Application.ScreenUpdating = False, you're telling Excel "don't repaint yourself until I say so" - that can speed things up considerably, in a lot of cases, however it also means you need to toggle it back on manually if something bad happens.
You can avoid this by implementing an error handler - here's the principle:
Sub DoSomething()
On Error GoTo CleanFail
Application.EnableEvents = False
Application.ScreenUpdating = False
'...code...
CleanExit:
Application.EnableEvents = True
Application.ScreenUpdating = True
Exit Sub
CleanFail:
Debug.Print Err.Description
Stop
Resume CleanExit
Resume 'F8 takes you to the error-throwing statement
End Sub

Answer 2

You have not indicated what sheet is the activesheet that has the worksheet_change event.
Any way, here is a code to find the last row in column B sheet "Projects"
Dim LastRow As Long, sh As Worksheet
Set sh = Sheets("Projects")
LastRow = sh.Cells(sh.Rows.Count, "B").End(xlUp).Row
MsgBox LastRow & " is the last row in Column B Sheet Projects!"