[Closed] shifting animation keys

Hi,

I have 200 planes and gave them them all the same animation. With the following code I can shift the animation keys of each plane:

for i = 1 to selection.count do
inserttime selection[i] 0 (i*2)

But how can make them gradually go faster; not consequently a 2 frames delay but beginning with 20 and ending with 2 for example? And does anyone know how to reverse this so that the last plane begins and the last plane ends? It should be quite simple, but I can’t figure it out.

Many thanks,

Theun