Restrict node by quantity already assigned to date (CCK Date field)?

I’m building a work schedule utility for my department, to track a specific task type. I’m nearing completion, but one bit of functionality eludes me. One of the requirements is the ability to restrict the creation or modification of a content type by the quantity assigned to a particular date.

In other words, if 10 nodes are already assigned to 12/16/2009, I need to disallow the creation of new nodes until an alternative date is selected. I can go with either a pure node quantity, but the preferable method would be to perform an additional calculation based off of a “Manhour” field. EG: Restrict the creation of the node because all available manhours have been reserved by the previous nodes.

Anyone know of any modules or techniques I could use to accomplish this functionality? I’m not even sure what kind of search terms to search by, as this seems like a niche need. Everything I've used so far has resulted in E-Comm cart solutions. I’m using CCK Date to assign the date field.