First you need to know what the animation frames are for the character. Then you check if the crouch button was pressed, if it was you use
Play Object (runs the animation once) or
Loop Object (If you want the object to loop the animation). Then if they use the movement keys you would have to run the frames that hold the running animation.
That should do roughly what you want.
If that was hard to understand here is some pusedo code that I hope makes it somewhat easier...
do
```Crouch animation
if scancode(crouch key)=1
Play Object character, crouch frame start, crouch frame end
endif
```Running Animation
```Forward
if upkey()=1
Loop Object character, run frame start, run frame end
endif
```And so on...
sync
loop
Hope that helps