How to use the FIFO cost while issuing ?

Dear Experts,

 

There is a client’s requirement which is explained below:

 

By using FIFO costing method, Item in the system is likewise:

 

Quantity        Cost         Date

50                     12        1-Jun-2013

100                   10          29-May-13

40                      5           25-may-13

 

Now suppose Items are required 50 Quantity. So while issuing from the subinventory by using Drop shipment it takes the average quantity of 10 & 5 = 0.1071

We have tested in the application that it selects the average cost while drop shipment. Can anyone suggest that is there any workaround or any other option to do so?

Thanks in Advance