Create Directory Tree

I've been trying my best to create a directory structure using VBA and Excel, and have run out of patience on how best to do this. My goal is to create a directory tree containing 2 levels. The 1st level (Main Folders) will be named from data in Column A of an Excel Spreadsheet, the 2nd level (Subfolders) will be created from data in Columns B, C and D of the spreadsheet. I've been using the following code with success, but don't know how to create subdirectories:

Sub StartHere()
Dim rCell As Range, rRng As Range
Set rRng = Sheet1.Range("A1:A20")
For Each rCell In rRng.Cells
CreateFolders rCell.Value, "C: est"
Next rCell
End Sub

Sub CreateFolders(sSubFolder As String, ByVal sBaseFolder As String)
Dim sTemp As String
'Make sure the base folder is ready to have a sub folder
'tacked on to the end
If Right(sBaseFolder, 1) <> "" Then
sBaseFolder = sBaseFolder & ""
End If............