From FCKeditor Docs

To create a new resource type you should place the section below in your config.asp file. Note that the options you can use are described in the Built-in resource types section.

Example: You want to create a resource type MSdocs which will only have doc,ppt,xls extensions and be maximum 2 megabites large.

Set ResourceTypes(3) = DefineResourceType( _
"MSdocs", _
baseUrl & "MSdocs", _
baseDir & "MSdocs", _
2M, _
"doc,ppt,xls", _
"" _
)

The CKFinder will use all the resources types including the one specifies by you.

You must adjust the array definition to include your new resources:

Dim ResourceTypes(3)

If you want to limit the CKFinder to use only your resource type you must place it in the CKFinder_Config.Add "DefaultResourceTypes", "" field. Example:

CKFinder_Config.Add "DefaultResourceTypes", "MSdocs"