Dynamic dynamic component and keep internal geometry

I have a bracket to fit to different size equal angles. The two holes at each end remain the same distance from the edge and remain the same size. So I essentially want to stretch the middle so the bracket fits to different size equal angle.
Any suggestion how I best do this please?

you could make the bracket with two parts - one is the “end” with the hole. and the “span” which is the part you’re changing the length of. copy the end and flip it. see attached example.
example simple bracket.skp (149.8 KB)

example simple l-bracket.skp (192.8 KB)

note: if you need variable openings and positions check out pcmoor’s excellent tutorial on “hole” components.