I do not understand your requirement. Please keep in mind I do not know your data.
if {SBNewRet.Bill code} in ["Fall11","FY2012"] then 'Fall 11' else {@NULL}
if {SBNewRet.Bill code} in ["SPR12","FY2012"] then 'Spr12' else {@NULL}
would display 2 results per row.
Since you have data on multiple rows per student you cannot just do a count.
Since you have rows that fall into both categories you cannot just make a group or one response field and do a grouping or count on that.