ok, I seem to have worked it out.
I created a script called scr_delta_alarm. Inside it I put:
/// scr_delta_alarm(n);
n = argument[0];
return n * 1000000;
In my Objects Create Event I put:
delta_alarm = scr_delta_alarm(3);
In the Objects Step event I put Frostys code I found on the forum:
if (delta_alarm > 0) {
delta_alarm -= delta_time;
if (delta_alarm <= 0) {
instance_create_layer(x,y,"Instances",objBullet);
delta_alarm = scr_delta_alarm(3);
}
}
It works lovely. Thanks all.