[Gabriel]

procedure TFFullDiariDM.QHoresRCalcFields(DataSet: TDataSet);
var
 TotalMinuts,Hores,Minuts : Integer;
begin
 TotalMinuts := Round(SecondsBetween(QHoresRSurt.AsDateTime,QHoresREntra.AsDateTime)/60);
 Hores := Trunc(TotalMinuts / 60);
 Minuts := Trunc(TotalMinuts mod 60);
 QHoresRHores.AsString := IntToStr(Hores) + ':' + FormatFloat('00',Minuts);
end;

Saludos