FM to deallocate sales order item which created with reference to a contract

[zaidshekh123]

Hello Expert,

i have requirement that, one sales order is created with reference to a contract but in the contract's line no 100 has 2 qty and in sales order has 4 qty, this called over referencing, so when i need to reject that line, first of all i have to deallocate that stock using ARUNWB tcode, then only i can reject that line from Sales order, i want to automate that process, so need fm or bapi for deallocation.

Thanks in advance

zaid