John,

You'll need to change the rate table on the Assignment - not on the resource. By default, Project uses rate table A for all assignments.

I am not a programmer but to explain the processes. You'd need to set the custom field at either the Resource or Task level. If at the Resource level, you'd need loop through each resource's assignments and set the cost rate table.

You might get some more in depth help at the Programming forum for Microsoft project.

See: http://social.technet.microsoft.com/...ct2010custprog