I hope that will help you...
This works for me with the subdomain folder in the main folder of the website.
Step 0 : Make sure that you can access the relative parent folder path using your scripts
(IIS > Website Properties > Base folder > Configuration Button > Options tab > Check if not checked)
On your subdomain you can try this script :
Step 1 : Get the content of your asp functions file
Dim Fso : Set Fso = CreateObject("Scripting.FileSystemObject")
Dim File : Set File = Fso.OpenTextFile(Server.MapPath("../PathOfYourFuncFile.asp"), 1)
Dim FileContent : FileContent = File.ReadAll
File.Close
Set File = Nothing
Step 2 : Clear <% and %> in FileContent variable
FileContent = Replace(FileContent, "<", "")
FileContent = Replace(FileContent, ">", "")
FileContent = Replace(FileContent, "%", "")
Step 3 : Use the script in your current page
Execute FileContent
Step 4 : Try to call your functions and subs
If that works you can easily optimise the script to get a clear code.
(Sorry for my bad english)
Edit :
this will not corrupt html content returned by functions or subs. Files loaded have to be only asp not html content with asp scripts inside.
Function StreamReader(vFic, vCharset)
Dim oContent
Dim oStreamReader : Set oStreamReader = CreateObject("ADODB.Stream")
With oStreamReader
.Open
.Charset = vCharset
.LoadFromFile vFic
oContent = .ReadText
.Close
End With
Set oStreamReader = Nothing
StreamReader = oContent
End Function
FileContent = StreamReader(Server.MapPath("File2.asp"), "utf-8")
FileContent = Replace(FileContent, Chr(Asc("<")) & Chr(Asc("%")), "")
FileContent = Replace(FileContent, Chr(Asc("%")) & Chr(Asc(">")), "")
Execute FileContent