Easy...
Create circuit that can turn on and off bunch of LEDs based on
bit value of the memory location in the controller. Let controller
scroll the memory and make sure the speed depends on value
in another memory location. Create some sort of interface to
the PC and make sure controller and VB program running on
PC can use it to exchange data. To save on I/O count and wiring
try to use multiplexing. If you want to make large display, consider
using multiple LEDs to form one pixel. There are some prewired
LED clusters such as 5x7 etc. Make sure to take care of power
requirement for the unit. If the unit is going to be in non-accessible
location, plan on wireless or at least modem connection.