This is a tricky area, the first thing to remember is that you need to compare like with like so convert the current users name into a notesName and read each name from the security fields into notesNames for comparison purposes.
You get the current user from notesSession
dim s as new notesSession
set currentUserName = new notesName(notesSession.EffectiveUserName)
Each name you are comparing can be extracted from field item values
set editorNames = doc.editorNames
forall value in editorNames.values
if value <> “” then
Set editorName = new notesName(value)
This might not be realistic if you have too many names too compare against, you might need to review the whole security model as it might no longer be appropriate for the current application.