Update Picking Quantity using 'WS_DELIVERY_UPDATE_2' - URGENT

Hi Experts,

I am struck with an error in updating the delivery. I am using an rfc WS_DELIVERY_UPDATE_2 which is updating the picking quantity one for the first time in a delivery with two delivery quantity in a batch but when iam using it for the other one it is not updating the quantity. I think the parameters which iam passing to RFC might be wrong. I am using the rfc as follows:

CALL FUNCTION 'WS_DELIVERY_UPDATE_2'

EXPORTING

VBKOK_WA = WA_VBKOK

SYNCHRON = 'X'

DELIVERY = DEL_NBR

UPDATE_PICKING = 'X'

COMMIT = 'X'

IF_DATABASE_UPDATE_1 = '1'

TABLES

VBPOK_TAB = TAB_VBPOK

PROT = I_PROTT.

Please correct me if anything is wrong in the interface.

Any quick response will be appreciated & rewarded.

Thanks