I am looking for a way to stop manipulate evaluating an expression when certain constraints on the variables are not satisfied. The file i am using is more complex than the one i have attached but believe it should work in the same way. So in the test file attached, i only want manipulate to work when b>a is true, if a=b or a>b i want the manipulate window to just put up an error message saying something like "b needs to be larger than a".
In this example its not such a big problem, but in my more complex file if manipulate tries to evaluate the expressions when the contraints are not satisfied mathematica crashes.
I am hoping this is easy to do, i am just not aware of how to do it, i was thinking of using an if statement inside manipulate but have had no success with that so far.
Attachment: Mathematica Test MANIPULATE error message.nb, URL: ,