To overcome this, we can make use of "prompt method" -- with a multi-value selection option.

1. Create one button.

    

2. Create two fields -- category and doc_Readers, with the "computed" and "allow multiple values" options selected.

    

3. Under category field, select/enter the keyword option -- keyword document will be available.

    

4. When clicking the button in the second field, values will be populated based on the option selected in the first field.

Here is the code:

Sub Click(Source As Button)
Dim doc As notesdocument
Dim db As NotesDatabase
Dim temp As String
Dim newdoc As notesdocument
Dim newview As notesview

Set session = New NotesSession
Set db = session.CurrentDatabase
Set ws = New NotesUIWorkspace
Set uidoc = ws.CurrentDocument
temp=uidoc.fieldgettext("Category") 
Set doc = uidoc.document
Set newview = db.getview("Enter View Name")
Set newdoc = newview.getdocumentbykey(temp, True)

If uidoc.IsNewDoc Then 
returnvalue = ws.Prompt(PROMPT_OKCANCELLISTMULT, 
"Search Customer Codes", "Please select",
"" , newdoc.Doc_Readers) 
doc.Doc_Readers = returnvalue
Else
returnvalue = ws.Prompt(PROMPT_OKCANCELLISTMULT, 
"Search Customer Codes", "Please select",
"" , newdoc.Doc_Readers)   
Set item = doc.getfirstitem("Doc_Readers")
Call item.appendtotextlist(returnvalue)
Call uidoc.Refresh
End If   
End Sub