Function Module to get the Shopping cart Change values.

Any body know how to get the change values on the shopping cart.

For examplet shopping cart 1000000 line item 2 initially has the value12000$ and later changed to 24000$.

when i use the function module BBP_PD_SC_ITEM_GETDETAIL it is giving the current value 24000$

Is there any function module which will return the 12000$.??

thanks

Madhavi,