Problem filling a combobox with tabledata

Question

Hi to All,
I'm tried to create a Form with datagrid that use data from a table.
For example the table has this structure:
CODE   3   char
DESC    20 char
TYPE     1   char

The field TYPE has only the value A, B, C; I need that when the datagrid is populated, the column TYPE display:
FirstValue      IF  TYPE = A
SecondValue IF  TYPE = B
ThirdValue    IF   TYPE = C

How can perform this ? I hope in Your help in order to resolve my problem (exist a sample ?)

Thank You and Best Regards.