If I understand correctly, you certainly can.
If you are working in MIDP 2, I would advice you to base it on Form + CustomItem. What you need to do is to implement a component that can display multiple lines.
To display multi-line text on Canvas or on CustomItem, you'll need to implement a line breaking algorithm, break the
string you want to show into lines and paint the lines with alignment of your choice.
I think it is better to do it as Form + CustomItem because you will be able to use the platform title and thus preserve the UI style throughout the application. If you implement it on Canvas, you will have to draw the title too and this can be quite different on the various handsets and not easy to draw.
In MIDP 1 devices you'll be forced to base it on Canvas, but those devices have usually more simple title styles.
You can use standard commands in both cases, so this is not a problem.
Hope this helps,
Yuri