Module pool programming..

hi,

i am creating a ztransaction here , iam creating it in create , change and display mode transactions .

like VA01, VA02,AVA03.

in my ztransaction if the user what to go to change mode from the create mode what i need to do like pass the value of sales order to change mode transaction using

SET PARAMETER ID ..

please let me knoe the following steps how to call the data in create mode to change mode..its urgent

thanx.

vijay.