How do you get a specific CFrame value from the rotational values?

This is published on the dev-wiki Creates a CFrame from position (x, y, z) with an orientation specified by the rotation matrix [[R00 R01 R02] [R10 R11 R12] [R20 R21 R22]]

CFrames contain lots of variables and I really need to know how to grab a specific number from a cframe in order to make comparisons...

I know how to get the X, Y, Z but how do I go about grabbing the R01, R02 etc... then using that single number in a script.

Help would be appreciated.