Use the Extension property of the IIsMimeType object to specify the MIME type of the file name extension.
DirObj.Extension = String
<%
Dim DirObj
Dim MimeMapNode
Dim MimeMapList
Dim MimeMapEntry
Set Obj = GetObject("IIS://LH/MimeMap")
MimeMapList = DirObj.MimeMap
Redim preserve MimeMapList (Ubound(MimeMapList)+1)
Set MimeMapEntry = CreateObject ("IIsMimeTyepEntry")
MimeMapEntry.MimeMap = "Text/Plain"
Mime.Extension = ".log"
Set MimeMapList (Ubound(MimeMapList)) = MimeMapEntry
DirObj.MimeMap = MimeMapList
DirObj.Setinfo
%>