Is there a way to have parts at equal spacing in an assemble that will change as the assembly size changes?

I have a bunch of frames that will have 2 stiffeners, equally spaced, on each frame.

Is there a mate, equation, etc. to automatically divide the overall of the frame into 3 equal spaces, so that when

the frame size changes, the spacings will change at the same time?

Thank you in advance for your help.