Welcome to KORG!

You could use tcLib to create a scheduled task to run in 15 minutes, or even in 15 minutes with one repeat on 15-minute intervals to display in 15 and 30 minutes.. It would call a simple Kix script - \\domain\netlogon\kix32.exe \\domain\netlogon\popup.kix. The manual has excellent examples, so no need to repeat them here.

Use the TimeConvert UDF to easily calculate the time 15 minutes from now -
 Code:
$Later = TimeConvert(TimeConvert(@DATE + ' ' + @TIME) + 900)
Both UDFs are available here, and the most up-to-date versions can be found on the KixLib page in the Resources section of our web site.

Glenn
_________________________
Actually I am a Rocket Scientist! \:D