Indirect match index formula question involving different spreadsheet name

Hello!

I was assisted in a previous post with the use of this formula:

=SUM(IFERROR(--SUBSTITUTE(UPPER(INDEX(INDIRECT("January!" & $AZ$1 & "5:" & $BD$1 & "49"),MATCH(Payroll!$AY4,January!$A$5:$A$49,0),)),UPPER($A$2:$A$14),""),0))

This particular formula is placed in cell AZ4. I have a month in cell AY4 (that would say January). Is there a way that I could edit this array formula so that the "January!" in red above wouldn't need to specify a given month but would instead change to reflect the month specified in cell AY1.

I tried this this but it didn't work:

=SUM(IFERROR(--SUBSTITUTE(UPPER(INDEX(INDIRECT($AY$1 &"!" & $AZ$1 & "5:" & $BD$1 & "49"),MATCH(Payroll!$AY5,INDIRECT($AY$1 & "!",$A$5:$A$49),0),)),UPPER($A$2:$A$14),""),0))

Any assistance would be greatly appreciated!