dynamic data reference from other worksheets used in formula

Hello Excel Gurus

i am just trying to create a dynamic formula where user chooses his/her school and years folders in dropdown cells A1 and A2 and these two contribute in formula where data is exctracted from.
The problem here is that i dont know how to make concatenate or & working. if i implement the result of concatenate in formula it works fine

=IFERROR(VLOOKUP(OFFSET($A1,1,MATCH("School name",$1:$1,0))-1,'G:\schools graphs\School1\2014\Report\[Report.xlsx]Tab1'!$Y$2:$AV$120008,24, FALSE),"")

but not when it looks like that
=IFERROR(VLOOKUP(OFFSET($A1,1,MATCH("School name",$1:$1,0))-1,CONCATENATE("G:\schools graphs\",A1,"\",A2,"\Report\[Report.xlsx]Tab1'!","$Y$2:$AV$120008"),24, FALSE),"")

or that
=IFERROR(VLOOKUP(OFFSET($A1,1,MATCH("School name",$1:$1,0))-1,"'G:\schools graphs\"&A1&"\"&A2&"\Report\[Report.xlsx]Tab1'!"&"$Y$2:$AV$120008"),24, FALSE),"")

Any ideas on how to make it working?

Thank you for any help

I think the problem is not whether I enter it wrongly but if an use of concatenate formula is valid in this kind of nested formula

haven't used it before, so may need to do a little reasearch on that one. Thanks

I am affraid I can't use any add ins at work and it seems its a single solution for this issue...

Anyway I found what I was looing for in the following post:

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