Question

I have this module here that has is Workbook subroutine. I can’t for the life of me understand how the GenerateLimitSummary is ever able to run? Can someone please articulate the process flow here?

Private LimitBool As Boolean

Private Sub Workbook_SheetCalculate(ByVal Sh As Object)

    If LimitBool Then Exit Sub

    ' use conditional formatting to highlight limit breaches
    ApplyConditionalFormatting

    ' regenerate the summary limits sheet
    LimitBool = True
    GenerateLimitSummary
    LimitBool = False

End Sub

Answer 1

The author uses LimitBool to prevent a infinite loop/a stack overflow:

• Initially, LimitBool is False, therefore the remainder of Workbook_SheetCalculateis executed
• Now, LimitBool is set to True (after it was confirmed it’s not True)
• GenerateLimitSummary is executed. If this routine now for some reasons forces the workbook to recalculate, Workbook_SheetCalculate will be triggered again. However, as LimitBool is now True*, the second call to this procedure is now Exited after the first check. If it would not have this check, it would again call GenerateLimitSummary, which would then trigger the recalc, etc…
• After the GenerateLimitSummaryran, LimitBool is set back to False, therefore, it can ran again

(*) – it has a Module-wide scope, i.e. it keeps it value across the different calls, while a procedure-wide scope (=Dimmed in the sub) would create a new variable for each call