Hi

I have no doubt some-one will offer a simpler suggestion for this, but intil then, try this

1. add a helper column on Campaign (I used I) and copy this down...
=VLOOKUP(G3,'Campaign Charges'!$B$2:$C$7,2,0)*0.15
Then on Staff, use this, copied down...
=SUMIF(Campaign!$F$4:$F$26,'Marketing Staff'!B3,Campaign!$I$3:$I$26)