Using an OnCalcField with a query - mysql

Question

// accounts receivable
qAR.SQL.Clear;
qAR.SQL.Text := 'Select C.Lastname,C.Firstname,C.Address,C.City,C.State,C.Zip,' +
'C.Hercell,C.Hiscell,C.Phone,C.Code,' +
'I.Date,I.Clino,I.Date,I.ToBePaid,' +
'SUM(CASE when C.Clino = I.Clino then I.ToBePaid END) as nToBePaid,' +
'SUM(CASE when C.Clino = I.Clino and I.Date between :S0 and :E0 then I.ToBePaid END) as nCurrent,' +
'SUM(CASE when C.Clino = I.Clino and I.Date between :S1 and :E1 then I.ToBePaid END) as nOver30,' +
'SUM(CASE when C.Clino = I.Clino and I.Date between :S2 and :E2 then I.ToBePaid END) as nOver60,' +
'SUM(CASE when C.Clino = I.Clino and I.Date <= :E3 then I.ToBePaid END) as nOver90 ' +
'from Invoice I ' +
'join Client C on C.Clino = I.Clino ' +
'where I.Date <= :E ' +
'and I.ToBePaid <> 0 ' +
'and I.Active = true ' +
'and C.Code <> 1 ' +
'group by C.Clino ' +
'having nToBePaid > 0 ' +
'order by C.Lastname,C.Firstname';
qAR.ParamByName('S0').AsDate := dDate30 + 1;
qAR.ParamByName('E0').AsDate := dBillingDate;
qAR.ParamByName('S1').AsDate := dDate60 + 1;
qAR.ParamByName('E1').AsDate := dDate30;
qAR.ParamByName('S2').AsDate := dDate90 + 1;
qAR.ParamByName('E2').AsDate := dDate60;
qAR.ParamByName('E3').AsDate := dDate90;
qAR.ParamByName('E').AsDate := dBillingDate;
qAR.FieldDefs.Updated := false;
qAR.FieldDefs.Update;
oField := TBooleanField.Create( qAR );
oField.FieldKind := fkCalculated;
qAR.OnCalcFields := qARCalcFields;
qAR.DetailFields := 'Clino';
qAR.Open;
I have a calculated field Sel (boolean) define in this query. I want to click a button and have the Sel fields on all records to be set to TRUE and another button and have them all set to FALSE. What should the code of 1) the OnCalcField and 2) each of the buttons be?
Thanks,
Jim Sawyer