While pressing z:
It would consist of checking the distance between player and enemy..
If the enemy is within reach, depending on the behaviour you want to use, set either it's vector or angle towards the player or simulate pressing right/left/up/down..
Increase the sucking power (speed of the enemy towards the player) depending on the distance..
Shouldn't be that hard if you know a bit about programming with construct2
But seeing this is your first post, you might want to follow some tutorials first, just to get the hang of things..