refund to customer

[SRINIBAS]

i have an issue.
the client entered into rent agreement last year.he gave all the rent money in adv and accounting was done in the legacy system.on jan 08 he terminates the contract.so we have to refund him the propertionate adv money.and also offset the unearned revenue to that extent which lies in the balance sheet from the last year.how to make this in receivable module.
need urgent feed back.in our newly implemented receivable module there in no transaction exist for that customer
so how to offset unearned revenue a/c