All you might know is that you have uploaded a file called test.txt into a /textfiles/ subdirectory at you host.
To open that file you will need to know its exact physical location ( like c:\www\textfiles\test.txt ). It can be done with this function:
Function String_GetFullPath( strVirtualPath )
String_GetFullPath = Server.MapPath( strVirtualPath )
String_GetFullPath = Replace(String_GetFullPath,"/","\")
Use it like this:
sFullPath = String_GetFullPath("/textfiles/test.txt" )
File_OpenExistingFile ( sFullPath...