Okay - no takers so allow me to post what I have discovered so far.
I can access the controls in my aspx page using my Master Page, and the FindControl method.
To be able to do this, I can write code on the Page Load of the master page.
Create an instance of the Master Page's ContentPlaceHolder control.
Dim placeholder as ContentPlaceHolder
placeholder = Page.Master.FindControl("ContentPlaceHolder1") 'the value of the FindControl may change depending on the ID of your master page's contentplaceholder
Then, I should create an instance of the control i am looking for, say a Label control
Dim myLabel as Label
myLabel = placeholder.FindControl("lblNewPage")
Once found, I can make changes to the property of the control:
If Not myLabel Is Nothing Then
myLabel.Style.Add("font-size", "20px")
End If
Regards,