I need to put a alt+255 on a work of mine. My laptop has no number pad, nor does it has those special keys for FN (except f1-f12). So the only way I have to emulate a num pad is with the onscreen keyboard

So, I opened it, pressed alt on my laptop and kept it pressed, but '255" with the onscreen keyboard, and nothing happened. No other code works either...what do I do? And yes, I tried pressing alt on the onscreen keyboard+255 on the onscreen keyboard.