How do I reduce a sprite's health every second?

This sounds like an easy thing to do but I'm struggling...

I have 4 wall sprites. 4 enemy sprites spawn and walk towards those and attack them.

How do I get each instance to attack it's wall, and reduce the wall's health every 1 second?

I've tried a lot of different methods but can't get it working.

Screen below

Thanks!

Hi!

upload a example capx with minimun things to improve help

this have several ways to do and mostly depends on your style, with a example its more accurate to help.

Thanks for the help

Sorry. what's a capx?

I've got this file, is that the sort of thing?

dropbox.com/s/d94q1y9erpzu9gg/Alien%20Game.c3p

Sorry, should post the above example game works as expected after a bit of work. The aliens run along and then attack the fences.

If anyone could check the events and see if I've made any horrible newb mistakes, I'd really appreciate it.

Just bought Construct and I think it's amazing!