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This answer isn't really going to be specific to VB, but here are some problems you are bound to run into:
1) What do you mean by screen? Do you wan't the message to scroll across everything on the monitor (over other programs running, the taskbar, desktop, etc)? Do you just want to have text scroll across a vb window or dialog? If you were doing this in C you would be looking for the DC (device context) for the window (or desktop) you wanted to draw on. I assume you'll have to do the same for VB. Once you have the DC you want to draw on you can use basic text drawing functions to do the rest.
2) You are going to want to draw the text then erase it and draw it in a new place. If you don't care that the background gets erased (i.e. you are drawing on your own dialog/window, then you can probably do this easily. Otherwise you'll have to save the contents of what you overwrite and restore them, repeat ad nauseum.
3) You will no doubt see flicker in your application as the drawing, erasing goes. A better approach is to use double buffering -- erase and draw to something offscreen first and copy that data to the screen when you're done. This way you don't really erase what is on screen, you simply draw over it with the next iteration of what is offscreen.
4) Only erase/copy what you need, doing large block transfers (bitblt) can take a long time and there is no reason to draw over what you don't need to.
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