Issuing sales order stock to stock in transit

Hi Friends,

I have a MTO scenario as below.

Stock is produced and reserved for sales order through MRP.

Now this sales order stock to be transported to port( plant2) from the manufacturing plant( plant1) and from port it has to be sold to customer.

For this i have done as below.

Created STO and VL10B then VL02n.

But while doing PGI in VL02n, system tries to pick the stock from unrestricted stock but not from sales order stock.

So it shows an error " deficit of unrestricted stock".

Please suggest me to provide the provision to pick the stock from sales order stock to stock in transit.

Points will be rewarded immediately...

Advance thanks to all gurus...

Raju