how do i make a sheet number relative in a formula?
I am trying to copy a cell down a column. My formula brings in data from
another Excel file.
Everything needs to stay the same as I drag/copy the formula except for the
"sheet number"

For me each cell looks like this when I copy it down:
='Untitled:July Billing:[Billing Invoice.xlsx]Sheet1'!$B$3
='Untitled:July Billing:[Billing Invoice.xlsx]Sheet1'!$B$3
='Untitled:July Billing:[Billing Invoice.xlsx]Sheet1'!$B$3

I would like it to look like this:
='Untitled:July Billing:[Billing Invoice.xlsx]Sheet1'!$B$3
='Untitled:July Billing:[Billing Invoice.xlsx]Sheet2'!$B$3
='Untitled:July Billing:[Billing Invoice.xlsx]Sheet3'!$B$3

Thanks in advance