Entries of invalid values in area A1:B6 are to be prevented, in case of an error a respective message box to be displayed.
Insert the following code in This Workbook module.
Private Sub Worksheet_Change(ByVal Target As Range) Dim var As Variant If IsEmpty(Target) Then Exit Sub If Intersect(Target, Range("Calculating")) _ Is Nothing Then Exit Sub var = Application.Sum(Range("Calculating")) If IsError(var) Then Beep MsgBox "Please enter the correct value!" Target.Value = "" End If End Sub
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