I've created a dependent combobox as mentioned as this article. http://office.microsoft.com/en-au/access-help/basing-one-combo-box-on-another-HA001173058.aspx
However, the problem I'm having is that I'm trying to do this with a datasheet. When I specify the criteria as another field, it'll look at the first row's value instead of the current row's value. I'm willing to do this as a contiguous form as well, but don't know if that would help.