Implementing Control's Properties
Every control has few properties as default: Name, Left, Index, Tag, and more.
Our control will inherit those properties as default.
But we want that our control will have some properties that
he doesn't get as default, like Text - the text of the message box
that will pop when the user press the button.

Implementing Text Property
We have 2 occasions: when reading the Text property and
when changing the Text property.
The reading occasion occur when we want to
read the porperty that the user set.
For example if the user set the control Text property to "hello",
the reading result will return "hello".
Lets implement first the reading occasion.

Enter the following code to your form:

Dim TextVariable As String

The TextVariable will be the variable that holds for us the value of the Text property, therefore the String that will be inserted into the message box.

Enter the following code to your form:

Private Sub UserControl_ReadProperties(PropBag As PropertyBag)
    TextVariable = PropBag.ReadProperty("Text", "There is no message")
End Sub

The function above says: read the control's "Text" property.
If the reading yield nothing, set as default the Text property
to be "There is no message".
We called to read the Text property,
now we have to implement the reading method:

Public Property Get Text() As String
    Text = TextVariable
End Property