O.k
I think I got it. I have changed from a hard coded table to a OnStart collect to populate my Combobox. below is a sample of that collection.
ClearCollect(colSiteNav,{PTitle:"Incident Report",Scrn:ScrnRL})
OnChange of that Combobox I have the following.
Set(PageNav,Self.Selected.PTitle);Navigate(Self.Selected.Scrn)
Then in the DefaultSelectedItems of that ComboBox I have
LookUp(colSiteNav,PTitle=PageNav)
Then C/P this Combobox to all four pages, That way the landing page has the selected fill already highlighted.