In VFP 5.0 I seem to be having a problem with a subquery. I can run the subquery stand alone and it works fine. Please someone tell me what I'm not seeing.

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SELECT uniqueid,number,date,type,sn,payee1,document from incoming ;
where BETWEEN(date,Thisform.sdate.value,thisform.edate.value) ;
and number NOT IN (Select number from receipts ;
where BETWEEN(letterdate,Thisform.sdate.value,thisform.edate.value) ;
and lettertype = [I]) ;
order by number ;
into cursor curLetter NOFILTER NOCONSOLE

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Ideas?