type mismatch

hi,
i have a function here... the error is "type mismatch" (in red)
the EmpNo and Pass is a string
anyone can tell me what problem is tat plz?
thanks a lot~




Function verify_user2(vuser, vpwd) As Boolean

Dim rs_user As Recordset
Dim DB As Database
Dim strCriteria As String
Set DB = CurrentDb()

DoCmd.SetWarnings False
guser = ""
glevel = ""

strCriteria = "select * from [Security] where [EmpNo] ='" & vuser & "' and [Pass] ='" & vpwd & "' "
Set rs_user = DB.OpenRecordset(strCriteria)

If rs_user.EOF Then
guser = ""
glevel = ""
rs_user.Close
verify_user2 = False
Exit Function
End If

End Function