Yes, there's the event_perform() method:
event_perform(type, numb)
type: What kind of event this is (i.e. mouse click, step etc)
numb: What specific instance of the type (i.e. for a type of step, possible numb values are ev_step_normal, ev_step_begin or ev_step_end)
ex:
if (event_perform(ev_mouse, ev_left_button) == true)
{
//do whatever the left mouse button does
}
This is all found in the GM help file, under generating events. You'll find all of the constants that you can use in the parameters.
