greetings

In Sheet2, I have the following formula in cell F5, dragged down toF300.
=IF(F5 = "","", VLOOKUP(F5, Sheet1!$C$16:$D$135, 2, 0))

The users would benefit by being able to see all of the data in Sheet1 at a
glance. Currently, we have to scroll up and down to see data in C16:D135.

I'd like to break up this data in C16:D135 into smaller 'chunks', all
visible at once on Sheet1, as follows:
C16:D45, F46:G75, I76:J105, L106:M135

My problem is the syntax of the IF formula on Sheet2. What's the best way
to get the VLOOKUP to scan the 4 smaller ranges?

Thank you
Brian