Contingent Revenue Recognition

Hello, I have a RE best practice question. We received a 3 year grant ($150,000/year) and we typically record this as a pledge receivable and recognize all the revenue ($450,000) at the point of the agreement and reduce the receivable when the annual $150,000 cash payments are received. The curve ball is in the funding agreement, where the donor stated that any unused funds at the end of the grant must be returned, thus triggering my auditor to say this is a contingent gift and can not be recorded as revenues until the money is spent, thus no pledge receivable and the first (& subsequent) cash payment(s) must be recorded to an unearned income liability account and the revenues can only be recognized once the cash is spent. I am wondering what others do to track this in RE (do you track the full 3 year “pledge”) as well as do use the gift sub-type and G/L coding to put the cash gift into the unearned income account and manually record the revenues when recognizing the expense (in FE versus RE). Thanks!