Worksheet_SelectionChange Returns an error if the condition is false

I try to bounce a Form if the selection is in column 4 and only 1 cell is selected and the cell next in column 3 is empty

If the condition is true it works

But if the condition is false, an error comes out:

run time error '13': type mismatch,

On the if line

That's the code:

Private Sub Worksheet_SelectionChange(ByVal Target As Range)

If Target.Column = 4 And Target.Cells.Count = 1 And Target.Offset(, -1).Value = 0 Then

    C = Target.Offset(, -1).Address
    UserForm1.Show

End If

End Sub

Selection Change Disaster

The Two to Three Issues

You should use CountLarge instead of Count. If you select too many cells, Count will cause Run-time error '6': Overflow. Try it by selecting all cells on the worksheet (CTRL+A).

If you select a range in column A, the impossibility of calculating Target.Offset(, -1) will cause Run-time error '1004': Application-defined or object-defined error.

If multiple cells are selected then Target.Offset(,-1).Value will result in an array which can not be compared to 0 which will cause Run-time error '13': Type mismatch.

A possible solution

Private Sub Worksheet_SelectionChange(ByVal Target As Range)

    Const ColumnNumber As Long = 4
    Const ColumnOffset As Long = -1
    Const OffsetValue As Long = 0

    Dim C As String

    With Target
        If .Column + ColumnOffset < 1 Or .Cells.CountLarge > 1 Then Exit Sub
        If .Column = ColumnNumber And .Offset(, ColumnOffset) = OffsetValue Then
            C = Target.Offset(, ColumnOffset).Address
            UserForm1.Show
        End If
    End With

End Sub