I wish to onscreen (example only) select (highlight) say B5:B7, then (with
control key down) then select C10:C11; then run a macro that will produce a
MsgBox with:

"The Difference is 1,234.50"

B5 = 1,111.00
B6 = 2,222.00
B7 = 3,333.00 where B5:B7 total 6,666,00

and
C10 = 2,500.00
C11 = 2,931.50 where C10:C11 totals 5,431.50

Any help appreciated,,