There is a Free Negro Register for Bedford County 1803-1860, I transcibed. The original is at the Library of Va in Richmond. Unfortunately I didn't see any "Allen" or "Walden" surnames. You probably need to look at the will and deed books, and county court order books for that time period. If they were freed after May 1, 1806 there is a good chance that they were forced to leave the county.

Selma