I would like to create a Proforma Retainer Invoice and send it out for payment. I would then like to apply my billable hours for that project against that invoice until it reaches $0 - or if the billable hours goes beyond it will ask me to save the extra time as billable (or ask me to create a 2nd invoice.) Anyone using retainer for services - this is the missing piece in Zoho. Today; I have paid invoices and billable hours, but can not match them up.