Hi,
In your example in post #1 you used "startdate". I assumed that this was a named range (I mentioned that in my post).
If it isn't a named range, try using a range reference:
="Date Period from "&TEXT(MIN(C3:C10),"dd mmm yy")&" to "&TEXT(MAX(C3:C10), "dd mmm yy")
Adjust C3:C10 as necessary.
Hope that helps...