there are tutorials and documentation covering every aspect of this.
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enter a second condition that says only play animation when walking, ELSE(special condition) add another event that says if player is walking(invert this condition) set animation to standing
btw, if you post a screenshot of the code, or just the actual cap file itself
you can usually get very helpful help
Quick example.
http://dl.getdropbox.com/u/1646976/anims.cap
I'd suggest reading through Deadeye's platfrom school in the tutorials section of the forum.
Hope that helps.