How to overwrite a display value of the edit field

[ideveloper]

Hi all.

I have the following problem:

I have 2 data tables which represent the relation between the customers and the bonus codes.

Table A
BonusCode | recId

Table B
AccountNum | ArticleNum | TableARecId (as key)

Now I am trying to create a form containing the grid with the AccountNum, ArticleNum and the BonusCode. The BonusCode field should have a lookup function to the data in the Table A. When I get the value of the BonusCode with the display method I must create my own lookup method from zero to have the possibility to choose the data.

Could I instead include the TableARecId in the grid as the edit field and overwrite the show method to show the value of the bonus code???