I've created a dynamic range formula which shows as below:
=CONCATENATE("AC SalesRawData!",SUBSTITUTE(ADDRESS(1,C1,4),"1",""),":",SUBSTITUTE(ADDRESS(1,C2,4),"1",""))
Which gives me the range output "AC SalesRawData!CQ:DS"
I'm then referencing this range in an vlookup using Indirect as shown...