>How do I get a half-second difference? I am trying to define a latency value of 0.5 second.

I'm not sure if you're asking how to measure by tenths of a second, or cause the system to pause for half a second but this should answer both:

lnS = SECONDS()
DECLARE Sleep IN Win32API INTEGER nMilliseconds
=sleep(500)
?SECONDS() - lnS