Below is the current formula I have, however, I need to change some
criteria, which now requires a change in the formula. Still the same look up,
but if c8="Internal" then vlookup D3..E60, if c8="external" then vlookup
G3..H60, if c8="none" then do nothing. How would I change the formula below
to make it work?

=IF(C8<"yes","",IF(ISNA(VLOOKUP(A8&"-"&F8&"-"&G8,'Writing
Charges'!$D$3:$E$60,2,0)),"",VLOOKUP(A8&"-"&F8&"-"&G8,'Writing
Charges'!$D$3:$E$60,2,0)*I8))