Project Budget should create in 2 lines

Summary: HI All,

I have below requirement :

For my client while executing the project customer will give some amount to execute few tasks. so customer would like to track the budget in 2 separate lines.

Ex; Project A has the Cost budget of 10000

Out of 10,000 , Customer share is 2000 and remaining 8000 amount is my share

The requirement is to maintain these 2 lines in the budget and We should be having a validation( If you are doing task which is sponsored by the customer budget should effect the Customer share line from the budget)

Let me know the possible work around for the same