Do it like this:
Dim Sql as string
sql="SELECT qryExcess.sidstrNAME_IND,"
sql=sql+" qryExcess.sidstrGR_ABBR_CODE, "
sql=sql+" qryExcess.sidstrDUTY_POSN,"
sql=sql+" qryExcess.sidstrDY_POSN_QUAL,"
sql=sql+" qryExcess.sidstrAUTH_PARA_DSG,"
sql=sql+" qryExcess.sidstrAUTH_LINE_DSG,"
sql=sql+" qryExcess.sidstrPMOSD_ENL ,"
sql=sql+" qryExcess.sidstrSMOSD_ENL,"
sql=sql+" qryExcess.sidstrAMOSD_ENL "
sql=sql+" FROM qryExcess WHERE (((qryExcess.orgstrPrNbr)sql=sql+" ='643')); "
Me!ExcessListBox.RowSource=sql
Note single quotes around '643'