get(current character) issue.

I'm trying to do a N-BACK experiment in matlab. each stimulus timing is 1 second. and the only key that is allowed to be pressed is 'L' and 'S'. I managed to limit the keys without timing the stimulus. so only if I press L or S it will move onto the next picture (stimulus). I managed to make the stimulus appear for 1 second but when I get the key that was pressed it moves the figure behind matlab so it's working on the background.(I used get(current character))

so first of all , how do I solve the figure jumping to the back of the screen? and second... what i'm trying to do is

while toc<1
and here I want to put the code that seemed to work with the key limits before..
end

does that make sense?

thanks, eran.