Visual Studio Build Definition - How to add additional (dll) files to build?

We have an asp.net c# web site in team foundation server. Our project includes a number of 3rd party dll's, that are located under bin/ folders of all developers. We are trying to adapt a build strategy, by using build definitions in tfs.

We tried to build the project in a different server than a develeoper computer, and the build failed, since these dll's do not exist there.

My question is; how do we put those dll's to build definition?

Hope I made myself clear, since we are apparently novices in tfs build services :)

Thank you all.

How do I reference a DLL in Visual Studio C++?

In Visual C++, click the Browse tab in the Add References dialog box. Click Browse, locate the component that you want on your local drive, and then click OK.

Thank you for your answers. Actually, we studied on it further and found a solution as follows:

Put dll's into _bin_deployableAssemblies folder under web application (name of this folder is important)
In the MSBuild Arguments part of the build definition, add /p:ReferencePath=""

That solved the problem. Thank you again in advance.