I need to change stage.frameRate, but how to keep tween speed?

Hello. I am using Flash CS6.

Right now I am trying to keep fps of tween motion.

I mean, I made a button that  speeds up and down stage.frameRate, if I click the button it does stage.frameRate +=1 or stage.frameRate -=1, but if stage framerate changes, it speeds up the tween animation too.Is there anyway to keep the speed of tween animation?

What I want to do is there are 2 movie clips, mcA and mcB, and mcA animation is dependent on stage.frameRate, if I click the forementioned button to change stage framerate, it also changes mcA framerate, but I don't want to change mcB framerate.There is a tween AS, it moves "mcB.x = 0" to "mcB.x = 100" in 10 frames with tween.I want to keep the pace of the tween animation.

Please give me your advice.