You need to create a mask for just the text. You can do this when you convert the text to a bitmap, it's one of the options given you.
From there it's not particularly intuitve. That's because the word 'mask' is used in two different contexts. The first, as in the mask created by the rasterization process is mask as in limiting an object with another object, as used in the Arrange->Mask function. The second is a bitmap mask which is used to protect areas of a bitmap from change, this is often called a marquee. You need to unmask the bitmap you just created using the first context of 'mask'. Select the masked bitmap and do Arrange->Unmask. Then turn the object that was used for the mask, first context, into a bitmap mask on the newly created bitmap, second context. Place the mask object on top of the bitmap [stacking order], select both the bitmap and the mask object and do Bitmap->Convert Object to Marquee.
Now you can Eye Candy away at it. When you're done, you can either remove the marquee or convert it back into an object, perhaps saving it for later or something, with various functions on the Bitmap menu.
You can also do pretty much the same thing with the magic wand bitmap mask tool but it's not a precise as creating the mask with the bitmap.
