SUPER URGENT!!!!!

I REALLY need some help!
How can i make my graphic animate across the screen?!?!?!!
Right now im thinking...

Data ........
Data ........
xlength = 30
ylength = 30
for y = 1 to xlength
for x = 1 to ylength
movex = movex + 5
cls
READ z
PSET (x + movex , y), z
next x
next y


BUT, it just sends one line here, another line there, and another line there! How do i fix this?