Display boundaries or depth question

I have a question about displaying an object only inside of a certain portion of my swf. My artboard is 550 by 400 but I want any edge of the object to only display inside of an area that is 400 x 300. It is ok if it exceeds that area but it should only display what is inside of that area. Basically so you only see the part that is inside of the area but not the part outside. I had someone tell me that would get me on the right track.

if (varname.x < 110 || varname.x > stage.width) {
// out of bounds horizontally
}
if (varname.y < 70 || varname.y > stage.height) {
// out of bounds vertically
}

Would there instead be a way to set the depth to the lowest layer of the swf, that way when I add the child I could set it to the lowest depth and I could build a frame to be on a higher layer and wouldn’t have to worry about it? I’m all about the quick and easy.