I have designed a search for that i use to search a  ProjectNo and the search function works perfect but i have ADD button that adds a value to the list box so i can search that value on a fly. but it doesnt add the value to the list box im not sure why.
the code for the the  Add button is as follows.

Private Sub cmdAdd_Click()
Dim SQL As String
    Dim CID As Long

    On Error Resume Next
    If IsNull(Forms!frmPLCProject1!ProjectID) Then
        MsgBox "No current customer record open"
        Exit Sub
    End If
    
    
    'To check if the record set already exist  in the list so we dontr have duplicates -------------
    
    CID = Nz(DLookup("ProjectID", "ProjNoSearchT", "ProjectID=" & Forms!frmPLCProject1!ProjectID), 0)
    If CID <> 0 Then
        MsgBox "Customer already exists in search list"
        Exit Sub
    End If
    
    With Forms!frmPLCProject1
        SQL = "INSERT INTO ProjNoSearchT (ProjectID, ProjectNo, Technician,) " & _
            "VALUES (" & !ProjectID & ", #" & !ProjectNo & "#, """ & _
            !Technician & """)"
    End With
    DoCmd.SetWarnings False
    DoCmd.RunSQL SQL
    DoCmd.SetWarnings True
    ProjNoList.Requery
            
    
End Sub