How do I add a variable row number into a SumIf formula cell reference

[Whit01]

How do I add a variable row number into a SumIf formula cell reference

I want to replace $100 cell references with a variable row number that I can locate using FIND.

SumIf formula where $100 needs to be replaced with a variable row number is:-

=IF(E10="","",SUMIF(Workings!$D$100:$F$600,'SAP Entry ex Misc'!C10,Workings!$F$100:$F$600))


Variable row number search is :-

Dim rngSearch As Range, rngFound As Range
    Set rngSearch = Range("A:A")
    Set rngFound = rngSearch.Find(What:="Vehicle totals...", LookIn:=xlValues, LookAt:=xlPart)

Thanks in advance for any help.