Doubt in Table controll

We are using one field of the the type of a dictionary field,which has value ranges , so that when we check the list box option, in the screen we are able to see two values in the drop down.

"ADD","DELETE".Can I add one more option ''REPLACE'' from the program, depending on certain conditions.I dont want to modify the value range, in the data dictionary.In some rows i want to put REPLACE.

Actually it takes values as A,D.and in the drop down we have like this

A add

D Delete.

If i m explicitly assigning R, only R is appearing.But how the description will come,as it comes from the dictionary.

i want the drop down to be

A add

D delete

R replace.

Again i m specifying this i want to achieve..with out modifying the value range in the domain.

Please help me out in this