I have the following code.

Do Until ActiveCell.Value = "End"
Range(Selection, Selection.End(xlDown)).Select
Selection.DataSeries Rowcol:=xlColumns, Type:=xlLinear, Date:=xlDay, _
Trend:=True
Selection.End(xlDown).Select
Loop

How do I make the loop stop when the selection doesn't find any more data?
At the moment it just goes to the bottom row of the workbook and fails.

I've kind of guessed how to make the loop happen in the first place and I'm
not that great (understatement) at VBA so help in simple terms would be
appreciated!

Many thanks