How to change Formula path referencing to the text inside a cell?

Hi, If the current Index/Match formula states:

"=INDEX('Y:\Brian\Payroll\[Payroll Commission P12 FirstSemi.xlsm]Payroll Summary'!$B:$B,MATCH(A2,A:A,0))"

How can I reference the "P12" to a cell let's say B2, which contains text "01"

The result will be
"=INDEX('Y:\Accounting Library\Brian\Payroll Commission\[Payroll Commission P01 FirstSemi.xlsm]Payroll Summary'!$B:$B,MATCH(A2,A:A,0))"

I tried to use INDIRECT formula which works but it won't work for a closed workbook that it's referencing to.

Please help, Thanks!