XX,YY mapping in excel

[Shado37]

I currently have a worksheet that tracks points in a chart in an xxx,yyy format. The cells go from:

A1: 001,001 to ALK999: 999,999

I have a list of coordinates that I want to color code within this grid that I pull from another area. So if I have say 650,650 that cell would go green (there are about 8000 coordinates to fill)

In my current design I have it all set as conditional formats however excel become lagged when run in this way and I want to be able to stream line it so it doesn't freeze every time I scroll. Looking for options. Any help is appreciated

 

[nuked]

Where does 650,650 come from?

 

[Shado37]

From imported data. Can be in the same workbook on another sheet