ORACLE FORMS-pop list index retrieval

Hi,
I have the following problem with a poplist.
a. Retrieve all the values and the list index(eg: 1,2,3) from the list item and store them in a pl/sql table.
b. When a value is chosen from the list,I need to get the list index from the list for that chosen value, and use that to retrieve the value from pl/sql table.

I am using retrieve_list to store the values and even the list index using a counter. But I am unable to figure out how to get the appropriate list index for the chosen list value.

Note - The label and value are same. Hence I cant use label as a list index.

Eg - for list item values 'a1','b1','b2','c3' , I want to store them in table as (1,'a1'),(2,'b1'),(3,'b2'),(4,'c3). And when 'b2' is chosen , I want to get 3 from the list, and use that to retrieve the stored value in the table.

I dont mind any other solution too where I can use numbers to store and retrieve values.

PLEASE HELP ASAP!!!

Thanks in advance
Madan