There is no hard fast rule that Im aware of though it seems that there is a general consensus that CGM can inhibit germination to one degree or another for roughly six weeks but the effectivness varies.

How much did you apply? and when?

You're close to being too late to drop seed already. The general rule of thumb is to allow 6 weeks before average first frost. If you seed tomorrow, you just barely make that. If you put down enough CGM for it to act as a pre emergent, I think you're better off waiting until there's snow in the forecast in the next day or two and put the seed down then for a dormant seeding approach.

Thanks,

Sounds like I should just wait for the dormant seeding approach. I put down about 40# on about 1000 sq ft of lawn, but from what I've read it may or may not act as a pre-emergent.

At 40# for 1000 sq ft, it will probably work as a pre emergent. Many people apply CGM for its pre emergent qualities but apply far less than the recommended rate. The original studies used fairly high application rates. The recommended rate is 20 lbs per 1000 sq ft, but that is below the rates in the original study. Many people apply at even lower rates and find that it doesn't do a good job.