Fix the value of accrual flag as 'Yes' when a user selects a particular transaction source

We have a requirement where we need to fix the value of accrual flag as 'Yes' when a user selects a particular transaction source for creating unprocessed cost.

e.g.- While creating an unprocessed cost in project costing module when a user selects 'project accrual' (dedicated transaction source to create accrual entries), it is a agreed that this will be an accrual transaction. Hence we want to default the value of accrual flag to 'Yes' as soon as user selects this specific transaction source.

Regards,

Amruta Manohar Bagde.