Macro loop not terminating

Hi i have a macro that is supposed to execute everytime something is changed on a sheet other than the summary one. the code is as follows

Private Sub Workbook_SheetChange(ByVal Sh As Object, ByVal Target As Range)
    Dim R As Long
    Dim C As Integer
    Dim num As Integer
    Dim lastrow As Integer
    Dim lastcol As Integer
        
    lastrow = Cells(Rows.Count, "A").End(xlUp).Row
    lastcol = Cells(1, Columns.Count).End(xlToLeft).Column
 
    num = 0
    
    If ActiveSheet.Name = "Summary" Then
        'Do Nothing
    Else
        For R = 2 To lastrow
            If IsEmpty(Cells(R, 1)) Then
                Cells(R, 2) = ""
            Else
                num = 0
                For C = 3 To lastcol
                    If IsEmpty(Cells(R, C)) Then
                        'Do Nothing
                    Else
                        num = num + 1
                    End If
                    Debug.Print ("Congratulationgs you've made it to checkpoint 1")
                Next C
                Cells(R, 2) = num
            End If
            Debug.Print ("Congratulationgs you've made it to checkpoint 2")
        Next R
    End If
End Sub

The problem is that the code will run and do what its supposed to. But then it won't stop and i have to break it to to unfreeze my excel program. any help?

you are changing worksheet during worksheet change event!

my untested revision:

Private Sub Workbook_SheetChange(ByVal Sh As Object, ByVal Target As Range)
    Dim R As Long
    Dim C As Integer
    Dim num As Integer
    Dim lastrow As Integer
    Dim lastcol As Integer
   Dim Debug_Mode as boolern
        
  Debug_Mode = true

    on error goto ErrorHandler
    Application.enableevents = false

    lastrow = Cells(Rows.Count, "A").End(xlUp).Row
    lastcol = Cells(1, Columns.Count).End(xlToLeft).Column
 
    num = 0
    
    If ActiveSheet.Name = "Summary" Then
        'Do Nothing
    Else
        For R = 2 To lastrow
            If IsEmpty(Cells(R, 1)) Then
                Cells(R, 2) = ""
            Else
                num = 0
                For C = 3 To lastcol
                    If IsEmpty(Cells(R, C)) Then
                        'Do Nothing
                    Else
                        num = num + 1
                    End If
                    Debug.Print ("Congratulationgs you've made it to checkpoint 1")
                Next C
                Cells(R, 2) = num
            End If
            Debug.Print ("Congratulationgs you've made it to checkpoint 2")
        Next R
    End If

   ErrorExit:
   Application.enableevents = true
   Exit Sub

  ErrorHandler:
  MsgBox "Error " & Err.Number & " (" & Err.Description & ") " 
  if degug_Mode then
   stop
   resume
 end if
  Goto ErrorExit
  
End Sub

Note: I added enableevents = false at the beginning and True at the end. Also addded ErrorHandler to ensure enableevents is always set back to true.

@ vandan_tanna
You will need
Application.EnableEvents = True in your ErrorHandler

ErrorHandler:
  Application.EnableEvents = True 
  MsgBox "Error " & Err.Number & " (" & Err.Description & ") "
  Err.Clear

This isn't required

ErrorExit:
   Application.enableevents = true
   Exit Sub

Marcol
if you don't have the errorexit part you'll get an error message every time

@Marcol:

I like single point exit. This is why in ErrorHandler I just show the error message and then go to ErrorExit where I reset the EnableEvents and exit the sub. For this particular example, only one item (EnableEvents) has to be reset, but in some cases a lot more needs to be reset. With my method, there is just one place - ErrorExit - where you reset everything, and you get to ErrorExit regardless of error! I guess is a matter of preference.

You solution will work also as long as you add exit sub before ErrorHandler (as JosephP pointed out)

why would you want to not handle errors? you can simplify to

Private Sub Workbook_SheetChange(ByVal Sh As Object, ByVal Target As Range)
    Dim R As Long
    Dim C As Integer
    Dim num As Integer
    Dim lastrow As Integer
    Dim lastcol As Integer
        
    lastrow = Cells(Rows.Count, "A").End(xlUp).Row
    lastcol = Cells(1, Columns.Count).End(xlToLeft).Column
 
    num = 0
    
    If ActiveSheet.Name = "Summary" Then
        'Do Nothing
    Else
        For R = 2 To lastrow
            If IsEmpty(Cells(R, 1)) Then
               on error resume next
               application.enableevents = false
                Cells(R, 2) = ""
                application.enableevents = true
                on error goto 0
           Else
                num = 0
                For C = 3 To lastcol
                    If IsEmpty(Cells(R, C)) Then
                        'Do Nothing
                    Else
                        num = num + 1
                    End If
                    Debug.Print ("Congratulationgs you've made it to checkpoint 1")
                Next C
                Cells(R, 2) = num
            End If
            Debug.Print ("Congratulationgs you've made it to checkpoint 2")
        Next R
    End If
End Sub

Apologies, a bit slap dash there ...
Another way would be

ErrorHandler:
  Application.EnableEvents = True
  If Err.Number <> 0 Then
    MsgBox "Error " & Err.Number & " (" & Err.Description & ") "
    Err.Clear
  End If