[Swftools-common] how to avoid loops ?

[Brainstorm]

I've made this simple sc script:

.flash name="pisamorena.swf" version=5 fps=25
    .jpeg pis "pisa.jpg" quality=80%

    .put pis x=0 y=0 scalex=50 scaley=50
    .frame 450
    .change pis x=0 y=0 scalex=200 scaley=200
.end

Now, how can I prevent this swf from looping forever ? I've been reading the 
swf file spec, but I'm lost, I can't see a field to specify the number of loops 
:-(

Thanks in advance !