Okay, so I'm doing something wrong.
I changed
DoCmd.OpenReport "rptManifestLetterToState", acPreview, , "ManifestDataIDPK IN(" & strWhere & ")"
to
DoCmd.OpenReport "rptmanifestlettertostate", acPreview, , "ManifestDataIDPK IN(" & strWhere & ")", , "ManifestDataIDPK IN(" & strWhere & ")" for...