Reading barcode data into sales order

Dear All,

My requirement is to read the material number (MATNR) from barcode through barcode reader and put the corresponding material number in sales order screen -va01.

I am Currently using this Functional module Exits CONVERSION_EXIT_MATN1_INPUT for this purpose.This FM has a input parameter and output parameter , The material number had to flow into input parameter and when pwe pass the same into output parameter the material number will be reflected in the sales order screen.

Now the problem is while reading material number is not coming into the input parameter , Please advice the reason behind this.

And please let me know if any setting to be done to read barcode.

Thanks and Reagrds

Praveen S