Adam - thanks very much for the walkthrough with examples.
The only issue with the circle is that I don’t want the white rectangle background to appear round the edge of the circle. Would I have to set the rectangle fill colour to the same as the background colour of my window? I can’t simply set it to be transparent as otherwise the level indicator would show through.
Your last example is almost exactly what I’m trying to achieve, with the exception again that I need to get rid of the white background round the edges.
Did you use an actual Cylindrical Tank control (rotated) to do that? Or did you draw your own elipses etc? Again I ask because I cannot use the Shape Difference function with the Cylindrical Tank control, only with shapes from the drawing toolbar.