Jumping Jack Flash

[Richmond]

One of the children on my Summer course was having 'problems' with 
animating a 'person'
to jump [ think "Super Mario"].

Well, I don't know what he is doing this weekend, but it took me all of 
15 minutes to knock together a basic walker-cum-jumper:

https://www.dropbox.com/sh/tyt4o1md51bfair/AABThCCgJkqLQvz1e-NRQGg7a?dl=0 File: 
Walker.zip

HOWEVER, there is a slight snag insofar as that having been bashing the 
left arrowKey, when I bash the up arrowKey (to generate a jump),
the character jumps, but then continues to execute the code stored from 
my pressing the left or right key for far too long than is
necessary.

The same thing happens if I press the left key repeatedly, then the 
right key once.

SO, what I need is some sort of INTERRUPT code so that when I press a 
new arrowKey all previous information fed by my key bashing gets lost.

Richmond.