Update grid with referencegroup field

Hello

I wanna update value in grid with referencegroup field. I lost selected checkboxes after refresh grid. Is any solution to don't lose selected  checkboxes ?

Below my update code: 

TaxTrans taxTrans;
Object taxTable_ds;
MultiSelectionHelper helper = MultiSelectionHelper::createFromCaller(caller);
;

taxTable_ds = formDataSource;
helper.parmDataSource(taxTable_ds);
taxTrans = helper.getFirst();

if (taxTrans.RecId != 0 && codeTaxReturn != 0)
{
while (taxTrans.RecId != 0)
{

taxTrans.CodeTaxReturnTableId_KP = codeTaxReturn;
taxTrans.update();
taxTrans = helper.getNext();
formDataSource.reread();
}
}
else
{
warning("@KVA57");
}

formDataSource.refresh();