Custom Header Update Macro

I have a case where my SS may have a number of TABs (named and unnamed{sheet 1,sheet2 etc}) - I have to use Headers (same header every tab) and it seems that I am always having to update them (change the date, change the project name etc etc)
I want to have a sheet that allows me to put the values and update all the tabs. I've included a sample and my requirements are:

1) The values in the yellow blocks (On the sheet) would be entered at initial, update/review time
2) They need to update ALL headers on All tabs (so I need to be able to address the tab whether I named it or not - All existing Tabs get header)
3) Need to get it so when I concantanate fields and one is a date field - I get the Date not the code for the date
4) Need to get it so when I concantanate fields , I can have Hard returns to make multiline entries into the header

I've figured out how to update the header of the active sheet - but not how to get them all - especially when I add new sheets -

I'm using :

 
Sub CellHeader()
Sheets("Sheet1")  *** need to select ALL sheets existing
Select Range("this is my concantaned fields") 
Select ActiveSheet.PageSetup.LeftHeader = ActiveCell.Value
End Sub