' Возвращаемое имя
Public AddedUser As String

Private Sub Form_Activate()
    txtUsername.Text = ""
    txtUsername.SetFocus
    AddedUser = ""
End Sub

Private Sub cmdOK_Click()

    Dim user As String
    user = Trim(txtUsername.Text)
    
    If user = "" Then
        MsgBox "Enter username.", vbExclamation
        Exit Sub
    End If
    
    AddedUser = user
    Me.Hide   ' НЕ Unload!

End Sub

Private Sub cmdCancel_Click()
    AddedUser = ""
    Me.Hide
End Sub

Private Sub txtUsername_KeyPress(KeyAscii As Integer)
    If KeyAscii = 13 Then
        KeyAscii = 0
        cmdOK_Click
    End If
End Sub