Raúl:

ComboBoxes are designed to return character values, not numeric, if you change you ID's type to character it will work the way you want. I understand that this is a mayor change for you at this time of your project, but as I see it, you will have to take this step. If you have a workarownd solution please let me know, I had a smilar problem but I opted to change all my projet ID's types to character.