Question about a driver rotation expression so I have a character with a skirt that's rigged. The skirt is positioned much higher up than the leg so once her leg/thigh reaches a certain height, I want her skirt bone that I have set up to also start rotating. I've managed to get the matching rotation occur with drivers, but at the moment I'm trying to set up an IF statement with the intention of: if the thigh bone is rotated 30.1 degrees on the Z axis, then start rotating (it would 30.1 or higher). I don't know much python, I do understand the fundamentals of creating variables and then plugging them into expressions which will then be evaluated.
Here's an image of my current driver setup

I'm a bit lost at this point, I have a value Zrt that perfectly represents the thigh bone's rotation and so once Zrt reaches a value of 30.1, then the dress bone would begin it's rotation.
Thank you in advance
Rotating how much?  What about when thigh bone isn't rotated that much?
The form of a single line &quot;If&quot; is something like the following:
((var * constant1) * (var&gt;(30.1 * pi/1800))) + ((var * constant2) * (1.0- var&gt;(30.1 * pi/180)))
What that's saying:
a) If var's rotation is greater than 30.1 degrees, output var * constant1.
b) Else, output var * constant2.
Constant2 can be zero.  You can understand this by recognizing that a statement like var&gt;n returns 1 if the statement is true and 0 if it is false.  Multiplying 1.0 - whatever instead of flipping &gt; for &lt;= is just style in this case, but it's style informed by the situations where the things you're measuring aren't exactly 0 or 1.
And the reason for var&gt;(30.1*pi/180) is because, for drivers, you're working with radians, not degrees.  (Don't ask me why, it's a developer decision than I don't necessarily agree with.)