Emulating PanelView, etc. OIT Num Entry notification

I need to be able to duplicate the notification / handshake functions associated with the PanelView’s numeric entry field in a legacy conversion project (at least the notification part).

Since I am using a touchscreen PC, I will have no keyboard, thus cannot trigger off of the enter key keycode.

What I need is a way to energize a bit when the numeric text (entry) field, after bringing up the touchscreen keypad, updates its value register when the touchscreen keypad’s “OK” key is pressed. The bit will then be used to advance a sequence in the plc to act on the new value.

Any ideas? I could watchdog the numeric text register in the PLC, looking for a value change, but that doesn’t work if the same value is entered twice. As far as clearing the PLC value after a new number is entered, that won’t work either, because in several cases, I will be using this for setting the slope and offset of some of the sensors (temperature, pressure transmitters), so some of the values entered will be zero (low calibration value for pressure transducers, load cells, etc).