API access to fileExtLinkTxtID

I'm looking for API access to the dbFile.fileExtLinkTxtID field (for reading, might need writing as well). Peter Barnett mentioned it should be there, but I can't see any obvious candidates in Object Browser for v4.5.0.26 of OMS.Library.dll. Any suggestions?

I couldn't find it either so use:file.GetExtraInfo(“fileExtLinkTxtID”);