The script damages the player? That is strange, could be a bug? have you tried maybe using g_PlayerHealth + 100 instead?
Also for the panel command, for example if you wanted to create a box in the lower left corner of the screen you would type: "Panel (2,74,12,97)"
The first two numbers are the upper left corner of the panel, and the second two numbers are the lower right corner of the panel. (I think)
EDIT: I've just given your script a run and it works for me, as in it healths the player. Did you want it to heal just a flat 100 health or constantly heal when E is held? because thats whats happening. If you would like it to be used once, call destroy(e) after the AddPlayerHealth(e)