Disable message box pop up only when user amending the existing value - vba

Question

I have vba code which pops up msg box if the entered value is zero. if the user later wants to change the zero to some other number it will still pops up the msg box before it allows to edit the zero to some other number.
I don’t want the msgbox pop up if user is changing the existing value.
Private Sub Worksheet_Change(ByVal Target As Range)
Application.EnableEvents = False
If Intersect(Target, Range("b4:af18")) Is Nothing Then
If Target.Value = 0 Then
Application.EnableEvents = True
MsgBox "This is it", vbApplicationModal, "Scikess/Holiday"
End If
End If
Application.EnableEvents = True
End Sub

Answer 1

I believe you are describing a situation where the user taps the delete key before typing in a new answer. In that case the blank cell has a numerical value of zero and you are getting a false positive on the check to see if the user typed in a zero.
Private Sub Worksheet_Change(ByVal Target As Range)
If Not Intersect(Target, Range("b4:af18")) Is Nothing Then
On Error GoTo bm_Safe_Exit
Dim trgt As Range
Application.EnableEvents = False
For Each trgt In Intersect(Target, Range("b4:af18"))
If trgt.Value = 0 And trgt.Text = "0" Then
MsgBox "This is it" & Chr(10) & trgt.Address(0, 0) & " cannot be zero.", _
vbApplicationModal, "Scikess/Holiday"
Application.Undo
trgt.Activate
Exit For
End If
Next trgt
End If
bm_Safe_Exit:
Application.EnableEvents = True
End Sub
I've attempted to have the code run when more than a single Target is involved (e.g. a paste or fill operation) but this makes the Application.Undo difficult to keep the other valid entries. Leave a comment on this behavior if it is unsuitable.
It also wasn;t clear on what range you wanted this to react on. You seem to have missed the Not in your Intersect method, making it react on any cell that wasn't in the range. I've adjusted above to include the range you specified, not exclude it.