A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data
You show the formula of F44 but not of F45. If it is similar, try something like
=$C$45-IFERROR('1004_Grid_Download'!$J$24, 0)
or
=IFERROR($C$45-'1004_Grid_Download'!$J$24, 0)