Question: How to prevent further execution of a worksheet if a condition is not met

My worksheet carries out some preliminary checks and if these fail I want to prevent or cancel any further executuon of the worksheet.  Something like (pseodo-code)

llContinue = DoThePreliminaryChecks()
If Not llContinue
    Cancel/Return/?
EndIf

I couldn't find anything in the docs or with Google.  Any suggestions?  Thanks.

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