On a elevated command prompt run this....

        runas /u:<domainB>\<username> /netonly mmc

On prompt.. type your domainB password.

Click File --> Add/Remove Snap-in
Choose Active Directory Users and Computers (from left side pane)
Click Add >
Click Ok

On the Console Root tree (it is on the Left hand side of the snapin)
Click Console Root --> Active Directory Users and Computer
 -- It may show an error dialog saying invalid creds etc.
Right click on it  and select Change Domain Controller... menu
On Change Directory Server dialog
    .. Select "This Domain Controller or AD LDS Instance" option
    .. On the first row of the table... click your mouse (or press F2) this should make the box editable
    .. Type the DC name
Click Ok