[AccessD] Field Entry question

I have a subform based on the following sql statement

 

SELECT [20ACCTEXT].MEMO_KEY, [20ACCTEXT].MEMO_LINE,
Left([Memo_Key],5) AS IncNum

FROM 20ACCTEXT;

 

When I try to enter a new record I get an error saying
IncNum (a hidden field used as link to parent records) is an
expression and con not   be edited.

 

If I manually clear the two errors generated everything
continues ok. Is there a way to suppress the two errors.

 

Thanks

 

Joe Hecht

jmhecht at earthlink.net