In reply to Gene Mroz.

THat's an interesting question, but it is might not be well defined. Either a distribution is CSR or it isn't. I don't know what it means to "approach" CSR. For some thoughts about testing for CSR (which assumes that the area is KNOWN), see "Divide and Count: A test for spatial randomness."

Perhaps you are looking for a region in which the density of events is high, but that is a different question from CSR. For some thought on high-density regions, see "Compute highest density regions in SAS."