Look Up Value with Fallback result

Anonymous here is the fix and the output:

LookupValueWithFallback = 
VAR CurrentDate = MAX('Combination Table'[Date]) // Replace with your actual date column
VAR CurrentRegion = MAX('Combination Table'[Region]) // Replace with your actual region column

VAR LookupResult =
    CALCULATE(
        MAX('Lookup Table'[Rolling Headcount]),
        FILTER(
            'Lookup Table',
            'Lookup Table'[Date] = CurrentDate &&
            'Lookup Table'[Region] = CurrentRegion
        )
    )
VAR FallbackDate = EOMONTH(CurrentDate, -2) + 1
VAR FallbackResult =
    CALCULATE(
        MAX('Lookup Table'[Rolling Headcount]),
        FILTER(
            'Lookup Table',
            'Lookup Table'[Date]= FallbackDate &&
            'Lookup Table'[Region]= CurrentRegion
        )
    )

RETURN
    IF(
        NOT ISBLANK(LookupResult),
        LookupResult,
        FallbackResult
    )