Thanks a lot!

Having had a played around with radial wipes etc I have managed it - however I did also find that you can draw on a layer with the paint brush and it records it in real time.

This would word great if you had a graphics tablet - but not so hot if you have only a mouse (unless you are exceptionally skilled in drawing with a mouse)

You can do it by opening the layer (double click on it in the timeline) selecting the brush tool and then in the paint pallette select "Write On" in the Duration pop up menu.

Then all you have to do is draw what you want to draw onto layer, then watch it back.