confusing subject for a confusing problem!

i have one scene with 4 buttons. what i WANT to have happen is, no matter which of the buttons you click, A, B, C, or D, you automatically go to frame, say, 500 of the scene.

at frame 500, a little animation plays.

when the animation is complete, you're sent to a different scene, depending upon what button you originally clicked. button A would send you to scene A, button B to scene B, etc.

but all of those buttons must first pass through the same frame 500 of scene 1.

its annoying and ridiculous, and sounds like it could be avoided or duplicated, but because of fluid animation in this case, it cant

any help?