In general, this functionality already exists.

If you need to browse a Lan Manager domain, or are having problems browsing a multi-domain environment, use Regedt32 to navigate to:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters

On the Edit menu, Add Value name OtherDomains, as a REG_MULTI_SZ data type. Enter each additional domain name that you wish to browse as a separate line.

NOTE: See tip 3180 ยป My Windows 2000 domain browse list is missing one of my domains?