Issue with IF(ISERROR(VLOOKUP syntax

Hello

I am working on combining two templates into one and am running into a roadblock. The below formula is working for me, but some cells do come back with a #N/A. How do I incorporate ISERROR or ISNA functionality into the below logic?

IF($G8=stkcost1!$B$1,(VLOOKUP($F8,stkcost1,MATCH($M$6,stkhead1,0),0)),IF($G8=stkcost2!$B$1,(VLOOKUP($F8,stkcost2,MATCH($M$6,stkhead2,0),0)),IF($G8=stkcost3!$B$1,(VLOOKUP($F8,stkcost3,MATCH($M$6,stkhead3,0),0)),IF($G8=stkcost4!$B$1,(VLOOKUP($F8,stkcost4,MATCH($M$6,stkhead4,0),0)),IF($G8=stkcost5!$B$1,(VLOOKUP($F8,stkcost5,MATCH($M$6,stkhead5,0),0)),"")))))

Thanks in advance!
Jess