Hi Bubbidge
Try this way
Draw a box around your bitmap
Fill it with a colour
place that box at the back of the layer (arrange-order-back of layer or shift+PgUp)
now your bitmap should be on top of your box
grab both objects then arrange-shaping-back minus front
that should remove what is on the top of the layer (the bitmap) and remove that shape out of the box now remove colour fill, un-combine delete the box and (hopefuly) Voila
I hope this works for you it works for me in X3
Pls let me know how you go
BTW i'm completly self taught in Corel so if there is a better way pls tell us
as i'm always looking for advice on a quicker/easier way to do things
Thaks Pep