flash actionscript

Is there such thing as a for/next loop in flash?

also, i was told that i can use "_" to create in index for of thing... but i dont know how to work it... basically im trying to do something like this

for I = 1 to 5
   box_I = box_I + speed_I
   speed_I = speed_I + 1
next

i only know a little vb6 and vb.net.... and honestly that doesnt even help because vb.net pulls away from indexing from what ive noticed.

LOOP:
LDY #4
LDA SPEED_L
CLC
ADC BOX_L
STA BOX_L
INC SPEED_L
DEY
BPL LOOP