Lien Waiver on Final Payment

I have a client that are not willing to pay us unless we reciprocally exchange check for unconditional release on final payment. We are located in California and I know that a Unconditional release will leave us without any rights if the check doesn't clear the bank. Are we allowed to add under Exceptions a note that states that this release is only valid upon funds positive deposit or something along these lines? thank you. Monica msafarik@icsinc.tv