For one thing, your code is on beginSprite which only happens once, when the sprite first appears. So, clicking on the checkbox will never change the volume unless you leave the frame and go to a frame tht this checkbox is not in, then come back. You probably want to also add some code to on mouseUp so that it adjusts the volume when it gets clicked.
Oh right, I have now changed it back to MouseUp but still nothing is happening.
I have also tried this if statement but it also has no effect
if (sprite("checkbox_Sounds").selected=1) then
put a few "put" statements into your code to see what is happening (or not happening)... for example:
on mouseUp me
... your other code here...
That will test to see if the button actually is getting pressed, and if the selected property is being correctly toggled... some Flash Component buttons don't work until you set the EventPassThrough to Always in the property inspector.
Thanks for the help Mike!
I'm finally getting to grips with Lingo now. I did make the silly mistake of having the component as Never not Always though :S