Create a Macro (tools/macro) first using this code:
 Sub WrapTextToggleButton()
marWrap = Selection.WrapText
Selection.WrapText = Not marWrap 
End Sub

After creating the macro above:
Right click on the toolbar and click customize 
under the commands tab \ categories column \ forms \ 
drag a button to your toolbar and right click on it 
to assign the macro you created above.