Calculating Running hours for devices in WINCC

Hi there,
i have some conveyors,elivators and valves. they are controlled by PLCs, the program was written by some other people, who did like this:
tag1 and tag2 (type BOOL) to show the running, alarm and out of service statuses.
if tag1 ==1 and tag2==0
then it means something for which it is assigned is running.

Now i want to calculate the Hours of running for there devices. i want to give a setpoint to PLC for running hours, then it should calculate upto that set point. if it exceeds that setpoint, an alarm should be triggered. can anyone give me detailed idea how to do all that stuff?
i am in urgency.
thanks and regards

Hi

If you have a lot of device to maintain it is better to use WinCC add-on PM-Maint, which is especially for this purpose. But if you have few device you can write a script which is triggered by tag1 & tag2, in the script calculate the running time as Nemo suggested and write it in a user archive. Each time you have to add the new time the old one.

Write another script which runs every hour, check the value in the user archive with the set point and create an alarm if necessary. You can reset the value of running time if you create the alarm.
Regards,
Mehrnosh