I am trying to do a lookup almost entirely based on the contents of various
cells.

I want to use the values sitting in B20 and C20 to get my range. B20 reads
'Sheet2!B80' and C20 is 'Sheet2!L98'. When I use
=VLOOKUP(A20;indirect(B20):indirect(C20);D20;FALSE ) then the formula bar says
my table array is volatile.

Has anyone any idea what I should be entering?

Thanks very much.