Calculating time difference - Wincc Professional V11

Hello,

I am developing a screen that shows the time used to produce an order, and later this information will be available in a SQL table.

To get this information in the first, I developed a VB script that "accumulates" production time in seconds and latter these are converted to the format hh:mm:ss, and this script was run by a "scheduled task "every second.

But that time is not accurate, I think the "Scheduled Task" is not so accurate, may depend on other factors (CPU load, for example) ...

So I think to "subtract" the actual time from the time the order starts would be the best solution, and this task be scheduled every second ...

Does anyone know how to calculate this difference of time using VB script?

Thanks in advance,

Hello Tweety, thanks for your reply !

I'm using Wincc Professional RT.

The second link you posted would be a good solution, but my intention is calculate the production time of an order just using Wincc Professional, because sometimes we integrate this supervisory in conjunction with "non-Siemens" systems, and I intend don't make modifications in a third-party PLC...

Best regards,