Contraint with "If"

can I add a contraint (or driver) that will work just If some variable is in in some value or values?
For Example: I want bone 1 to copy the rotation of bone 2 just if bone 3 is not rotated at all.


of course there are many ways to do that. You can for instance have the constraint’s influence be driven by any other value, or have the driver be multiplied by that value (1=on, 0=off).


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My earlier answer was misguided, I was thinking of some other problem. But yours is super easy, and yes, there is an ‘if’ for this.
Let’s say our bone 3 rotation is defined in drivers as rot3. (You will have to do this). Then your driver for the influence slider in the copy rotation constraint that copies the rotation for bone 2 to bone 1 would simply be rot3 == 0. This would give you an influence of 1 (full) when bone 3 has no rotation, and an influence of 0 (none) when bone 3 has any rotation on it at all.
I did a quick test and this worked, let me know how you get along.