Connecting to Folder/File to open mxd document using ArcObjects?

I have a dialog box written in ArcObjects.

I am programming the Map button on the dialog box.

The user picks a type of station and county.

The program goes to folder containing the mxds and opens the one with the same county name.

I need to know how to code for going to folder and then opening the mxd.

My program is listed below :

Dim pWorkspaceName As WorkspaceName
Set pWorkspaceName = New WorkspaceName
Dim pWorkspaceName2 As WorkspaceName2
Set pWorkspaceName2 = New WorkspaceName2

pWorkspaceName.PathName = "K:\TASS\4_MAPPING_DATA_Maps\2012"
pWorkspaceName.PathName2 = "K:\TASS\4_MAPPING_DATA_SUPPORT\Traffic_Mapping\Urban_Maps"

Dim cboStations As String
If cboStations = "Annual" Then pWorkspaceName.PathName
Else
pWorkspaceName.PathName2


Dim districts As String

Dim cboDistrict As String

If cboDistrict = "Abilene" Then Application.OpenDocument ("K:\TASS\4_MAPPING\Abilene_Base_Map.mxd")
Elif
cboDistrict = "Amarillo" then getmxd "K:\TASS\4_ps\2012\Amarillo"