I do this by making the container transparent (Set the Opaque property to False) and then place a rectangle in the container. Then you can round the corners of the rectangle using the circular handle on the rectangle's upper right corner. Set the layout on the rectangle to expand or contract in all directions and it will size itself with the container
When you have the container selected it is one of the available properties in the Property Editor. Make sure your properties filter is set to Standard or All.
the photo is also what i have now so it looks good only down side is that i have small overlay of back ground so i can't have 2 backrgound colors at once behind my container but that not that big of a problem.
Technically this is possible to do through scripting. Here is an example of doing this for a momentary button, it should be applicable to a container as well.
That code doesn't address the background, but that is also achievable.
I might be able to find some time today to work through that, shouldn't be too difficult.
i think i'll leave it with what i have now.
not good add scripting and i think it is indeed possible with script but not worth effort or time find out how it all works.
thanks for help anyway! if i had more time for the project i would look more into the scripting part of it!