BAPI_GOODS_MVMT_CREATE - for MIGO 101 movmt type with serial no on Delivery

Question

Dear Gurus,
Scenario
We have to transfer serialized Material from one plant to another via STO
ST order --> Delivery --> PGI (with Serial Number) --> MIGO at recieving plant.
For MIGO (101) movement we want to use BAPI_GOODSMVT_CREATE.
Now we have tried many combinations for it.
if we se GM_CODE = '01'. and Movement Indicator 'B' (for purchase orders) then it gives error "Maintain Serial number."
So if we maintaine serial number in thetable it says that you "cannot assign this serial number to the material "(AS the serial no is attached to the material at the time of PGI).
Now if we try to change the the movement Indicator to 'L' (for deliveries) we are getting the error "Update control of movement type is incorrect (entry 101 X X _ L) "
We have maintianed all necessary fields otherwise it would not give he Maintain srial no error (we think). I know this is very technical. but if anyone has prior knowledge please Help
Dany

Answer 1

Thanks for the reply.  The Price Control Indicator is 'S'.
The solution was set up at my company before I joined, but the different movement type is to enable the free goods stock to make a Finance posting to a Bonus Stock GL Account.  Bonus stock sale update the same account.
As I mention the '970' movement type worked fine with Goods Receipt against a Purchase Order (it was coded into to the user exit). 
The MM procedures were changed to use the Inbound Delivery matched to the PO, this had a result that when the Goods receipt was posted in MIGO it posted as 101 movement, as the PO number was not being recognised.
By making a further change to the user exit we able to suggest the '970' movement type, but now get the BORGR622 error I refer to.
'511' is not possible against an inbound delivery either.