Hi everyone. I need your help in a problem regarding Matlab.

I have created a simple gui (using matlab guide). In some point, at a specific callback of the gui I compute the a certain variable. I want this variable to be used by other callbacks. The problem is that if I declare this variable as "global" an error occurs. In particular the error occurs at the first usage of this variable (after the declaratio) and it is: unreference variable. How can I declare global variables in a m-file of a gui?

Any ideas???