Hi Olaf,
>upper(curTest1.cName) does not exactly match upper(cName), but you need to qualify which cName field is meant and rushmore still identifies it can use xName of curTest1.

with Alekseys trick UDF's are used for alias-identified filtering as well. Insert into Alekseys code:

select newData 
delete TAG F_1_2_new
index on Padr(myUdf1((Field1)), 20) + Padr(myUdf2((Field2)), 15) tag F_1_2_new
INDEX on PADR(myUdf1((Field1)), 20) TAG Filt_New

select oldData 
delete TAG F_1_2_Old
index on Padr(myUdf1((Field1)), 20) + Padr(myUdf2((Field2)), 15) tag F_1_2_Old
INDEX on PADR(myUdf1((Field1)), 20) TAG Filt_Old
?
lcVgl = PADR(myUdf1("x"), 20)
Select ;
    Nw.Field1, Ol.Field2 ;
    from newData Nw ;
    join oldData Ol ;
        on  Padr(myUdf1(ol.Field1), 20) + Padr(myUdf2(ol.Field2), 15) ;
          = Padr(myUdf1(nw.Field1), 20) + Padr(myUdf2(nw.Field2), 15) ;
    WHERE PADR(myUdf1((nw.Field1)), 20) = m.lcVgl ; 
INTO CURSOR res          

*-----------
select newData 
delete TAG F_1_2_new
DELETE TAG Filt_New
index on Padr(Field1, 20) + Padr(Field2, 15) tag F_1_2_new

select oldData 
delete TAG F_1_2_Old
DELETE TAG Filt_Old
index on Padr(Field1, 20) + Padr(Field2, 15) tag F_1_2_old

regards

thomas