FxGen

hello i am new here and i really like FxGen, even when the latest version seems to be more unstable as preview version. I have coded an own small texture generator some years ago and had a bad hd crash in the past when i lost all the stuff :( However i would like to have the operator "RoundRect" which may work like:

Generator_RoundRect( x, y, width, height, CornerWidth, CornerHeight, Color )

// x == coord of rectangles upper-left corner
// y == coord of rectangles upper-left corner
// width == of the rectangle
// height == of the rectangle
// CornerWidth == width of ellipse used to draw rounded corners
// CornerHeight == height of ellipse used to draw rounded corners

an example will be attached.

Does someone know how to code this effect and can post a working source? (psydo-basic would be nice)
Thanks in advance and keep on your great work guys! *thumbs up*