I'm seeking an example showing how to create a DLL that can be called from UnrealScript in Unreal Engine 1 or Unreal Tournament.
Unfortunately Epic seems to have removed most of the documentation for non-UDK versions of the engine from public view.
Archive.org preserved some documentation from how to do it within UE2 (which is probably closer to UE1 than UE3), but I can't turn up anything official for UE1 anywhere.
UnrealWiki has a Legacy Native Coding page, but many of the links on it are now dead.
Writing native code in many versions of Unreal, as well as writing Native Classes in UE3, requires a source license.
According to the UDN, that function was added to Unreal Engine 3 on December 2009's version, and wasn't made available for older builds. Looks like you're out of luck.