CorelDRAW Graphics Suite X4 :: Rounded / Radius Corners On Boxes And Rectangles

What I do not like is that I draw a rectangle and then add the radius corners and it is fine.

If I then drag the box taller or wider the radius of the corner changes too.  But also I have noticed that it does this even if you drag the box to size first then add the radius corners.

example:  I make up a rectangle and add start adding text.  Then I have to make the box bigger so I do that, finish adding my text.  Now go to add in the radius corner and they are all skewed out of shape.  This seems to be because I have dragged that rectangle bigger that what it was when I first dragged it into place.

Is there a way around this so that I can make my rectangle say 250 wide by 50 tall. Then later on change it's size and add radius corners and make it so the corners are all even and not all out of proportions?