All dba firebird...

I have table CLtrans(mydate,posting,win,lose,userd).
And this table have trigger :
Create trigger myposting before update on CLtrans;
Call posting();
End;

Create procedure posting();
.. Some proces...
Set _win=_win+1;
Set _lose=_lose+1;
End;

Can I update cltrans.win and lose at procedure posting??
Because I try
Old.win=old.win+_win
Error.

Thanks
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