Getting user input until they select the right choice

I have a code which requires the user to select a point on a plot. If they select a point that is not on the plot then it will keep asking the user to click on another point. Is the a way to do this? or something similar that I could work with?

Thanks

Answer 1

[per isakson]

Start simple. Hint:

    x = inf;
    y = inf;
    while is_outside(x,y)
        disp('select a point')
        [x,y] = ginput(1);
    end

where is_outside is a function with a couple of if-statements.

Cntrl+C works.