Below is a little something I cooked up on the fly when I've read your message. I won't be hold responsible if it's gibberish, as I haven't tested it (I only compiled it).
The way it 'should' work is that you use buttons 1 and 2 on the display. In my case they give out a 'true' signal as long as they're pushed. If out press on or the other than you start the generators which increment the value - thus leading to increasing or decreasing the output value respectively. You should bare in mind two things though:
1. you are limited to a output value of 255. This piece of code does not recognize an overflow - but that can be easily changed with a simple 'compare' block
2. it will go bananas if you press 1 and 2 at the same time (or it will just go with '1' command as it's higher on the block diagram) - but that can also be changed.
Thanks to w nice compiler, the start values are always set to 0 at the beginning of the program loop, so you don't have to worry that you'll get some crap at the beginning. But if you want to be extra sure, you can alway force all values to 0 at the first program loop.
Be aware that this is only a simple demonstration of how it can be done. Now depending on what you really want from it, is should be changed accordingly. For example you would want the counter to return to value '1' after you release the button. And so on. Hope it helps you.
Best regards,
Rafal
