Perdiem calculations for multiple locations with different statutory types

Dear Experts,

As part of the perdiem calculations, when an employee selected different statutory trip types for different dates in a trip duration,perdiem to be calculated differently.But i am failing to calculate to such type of perdiems.

For Example :

Trip duration is, say from 01.05.2014 to 10.05.2014

Statutory trip types X with amount 200/day, Y with amount 300/day

When employee select the statutory trip type for  01.05.2014 to 05.05.2014 as X

and for 06.05.2014 to 10.05.2014 as Y

As per the scenario

01.05.2014 to 05.05.2014 (5 days *200) =1000

06.05.2014 to 10.05.2014 (5 days *300) =1500

total perdiem amount to be 2500 for the total trip duration

But my system considering last statutory trip type in calculating total perdiem as 3000 for the entire trip.

Please provide your suggestions to meet the requirement mentioned above

Thanks & Regards,

Y.V.P.Deepak