Should this work? To make objects with interval. Once started and stopped it never starts again.
global cubes
register function:loader():interval 1
autocam off
set display mode 1024,768,32
set window size 1024,768
sync on
sync rate 60
sync
position camera 0,10,-100
make object box 1000,100,0.1,100 `a floor
do
set cursor 0,0
print "FPS ";screen fps()
print "Push I to start interval to make cubes"
print "Push S to stop interval"
if inkey$()="i" then start interval 1,1,250,0 `start interval with "i" to make cubes 4/sec
if inkey$()="s" then stop interval 1 `stop interval with "s"
sync
loop
function loader()
if register call() then exitfunction
inc cubes
make object cube cubes,6
position object cubes,rnd(100)-50,3,rnd(100)-50
endfunction