Cannot create New tab or button with VBA

We have created a routine in Project 2013 that should add a new ribbon tab and button using the following code:

Public Sub AddGuideRibbonButton1()
Dim myNavBar As String
myNavBar = "<mso:customUI xmlns:mso=""http://schemas.microsoft.com/office/2009/07/customui"">"
myNavBar = myNavBar + "  <mso:ribbon>"
myNavBar = myNavBar + "    <mso:qat/>"
myNavBar = myNavBar + "    <mso:tabs>"
myNavBar = myNavBar + "      <mso:tab id=""tools"" label=""Utilities"" insertBeforeQ=""mso:TabFormat"">"
myNavBar = myNavBar + "        <mso:group id=""myTools"" label=""MyTools"" autoScale=""true"">"
myNavBar = myNavBar + "          <mso:button id=""placeholder1"" label=""Hello World"" "
myNavBar = myNavBar + "imageMso=""DiagramTargetInsertClassic"" onAction=""HelloWorld""/>"
myNavBar = myNavBar + "        </mso:group>"
myNavBar = myNavBar + "      </mso:tab>"
myNavBar = myNavBar + "    </mso:tabs>"
myNavBar = myNavBar + "  </mso:ribbon>"
myNavBar = myNavBar + "</mso:customUI>"
ActiveProject.SetCustomUI (myNavBar)
End Sub

For some reason that is escaping me, the tab and button are not rendering.  We have enabled macros when entering project.  Hope someone might be able to suggest something.

Thanks