Continous Addition of a Constant

This has to be simple however I can't figure a way to do this.

If as a result of a calculation the number lets say is 3.

I want to add that number every second until a timer is complete.

So first second 3, second second 6, third 9 and so on .

The plc is an Idec Pentra.

Thanks in Advance

I could see using a second timer to count every second. Not sure how the Idec's work but I would assume the have a bit that gets set when a timer is done.

Set a second timer for a 1 second duration and do the math everytime the timer goes done. Have the same rung the math is in reset the timer.

You could set up a 1 second timer, and everytime it's done bit goes high your constant value gets added.
It could be enabled when your main timer starts, and use the main timers run bit to initiate the second timer.

Here is a sample for an Idec PLC. If there is any possibility that M0 will exceed maximum allowed value (65565), then you need to add a routine to handle overflow register when special internal overflow relay M303 is set. Also you need to add a rung to clear M0 to 0, and reset Timer T0 when you are done with the number.

Thanks

I used the two timer scheme and of course it worked fine.
Thanks to the responders much appreciated