Thanks for you response but it doesnt solve the problem.

SourceTable could have rows like:

ID SourceAmout

1 1300

2 2000

3 1700

and @AmountToAllocate passed to SP could be 4123.00

in this case I would like to insert records in AllocationTable like this

SourceTableID, AllocatedAmount

1 1300

2 2000

3 823

Additionally I dont want to reallocate the amount if it has been already allocated i.e rows exist in AllocationTable

Thanks again for your help

B.Syd