SetTimer, SwitchVirtualDesktops , 30000 
return

SwitchVirtualDesktops:

NextScreen++
If ( NextScreen = 1 ) {
 Send #1
}
If ( NextScreen = 2 ) {
 Send #2
}
If ( NextScreen = 3 ) {
 Send #3
}
If ( NextScreen = 4 ) {
 Send #4
 NextScreen = 0
}
return