How do I Scale a sprite object depending on its Y position?

I'm trying to make an object go from scale 1 on the bottom of the screen to scale 0.6 by the middle of the screen, with a smooth transition of course, i'm not a programmer by any means, so bear with me, this could be so easy but honestly.. I have no idea of how to make it work...

If the screen height is 480, then half of it is 240 and you can do this:

Set scale to lerp(0.6, 1, (sprite.y-240)/240)

awesome!!. works perfectly!!... but how would that same expression be if besides scale i would like to set the speed of the same object depending on the Y position?... i want full speed at the bottom of the screen and half speed at the middle of the screen...

never mind!... is "set maximum speed to lerp (slowest speed,top speed (sprite.y minus half the size of the screen/half of the screen"