Maya setAttr field enabled

Hy!

Since hours I try to solve a problem I have with Maya / MEL / Python. I have a script to set values of a fluid container.

E.g. setAttr "fluidShape1.densityDissipation" 0.2

Works great...

My problem: Actually it is not possible to change the value using the interface (see image). Is there a way to find out if the "text box" is enabled?

Thanks!!