Yes Deepak. The solution i thought might work is a mix of VOFM (where you create the routine) and VOTXN where you assign the new routine to the access sequence and assign access seq to the text type either on the billing header or on the billing item. The logic on the routine will depend on where you want to use the text type. (billing header Vs highest level Billing Item)
Hope this works.
Regards,
Mukund S