Changed it to:
=DSum(" [GRADES] * [ACT CREDITS] ",[Forms]![INDIVIDUAL APR]![BOX2],"[YEAR] = REPORTS![Main Report]![APR REPORT YEAR1].REPORT![YEAR] AND ([GRADES] LIKE '[0-9]*' OR [GRADES] = NULL )")/DSum("[ACT CREDITS]",[Forms]![INDIVIDUAL APR]![BOX2],"[YEAR] = REPORTS![Main Report]![APR REPORT...