Yes...flags will get the job done. Flags are a way to add a timming element to an event. See below (code not perfect format but you get the idea)
When DOOR NOT SECURE (DOOR is your zone name)
Then DOOR-OPEN ON for 10 seconds (DOOR-OPEN is your flag name)
When DOOR-OPEN OFF (your 10 second flag has expired)
AND IF DOOR NOT SECURE
Then beep all keypads
Then say DOOR STILL OPEN (DOOR STILL OPEN is the "message" to be announced over your keypad)
The way I'd do it would be to use three rules: one to start the timer when the door is opened, a second one to respond to the timer, and a third one to cancel the timer when the door is closed. This way, if you open the door, close it, but then open it again 10 seconds later, the message doesn't sound immediately. Name a flag called, say, "F Door Timer" in PC Access. Then you can write these:
1. This rule starts the timer.
WHEN Front Door NOT READY
THEN F Door Timer ON FOR 10 SECONDS
2. This rule runs when the timer goes off.
WHEN F Door Timer OFF
THEN SAY Door Open (whatever else you want it to do)
3. This rule stops the timer when the door is closed. Setting the value to 0 sets the flag back to "off" state without triggering the "off" rule above.
WHEN Front Door SECURE
THEN SET F Door Timer TO 0
(you can also put in rules here to cancel the noisemakers if you want)
This does not constantly beep like you wanted. I have not looked at the options for a continuous beep but you may need to sound an alarm to get that feature.
"ALL CONSOLES BEEP ON" does what you want.