How to write custom drc for solder mask aperture bridging nets

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I do a lot of RF work and have need for solder mask apertures over CBCPW (conductor backed coplanar waveguide). This aperture bridges the RF net and the ground net. This is by design. I would like to write a custom drc rule that says:

(rule “RF soldermask”
( constraint INSERT_SOMETHING_HERE)
( condition “A.NetClass == ‘CBCPW 50’ && B.NetName == ‘GND’”))

What is the “INSERT_SOMETHING_HERE” that I should put to tell it not to check the soldermask aperture between the netclass CBCPW 50 and the net GND?