Trying to understand Object Heirarchy

I am trying to get to grips with object heirarchy

Could someone please let me know why the following work/ don't work (as noted in the comments) before I loose my marbles completely - any insight would be appreciated:

Many thanks - Alastair

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Set AppExcel = CreateObject("Excel.Application")

set wBook = AppExcel.Workbooks.Open("Temp.xls")

Set mysheet = wBook.Sheets(1)

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wBook.WorkSheets(1).Select
wBook.WorkSheets(1).Activate

'These lines performs without error

AppExcel.Range("A2").Select
AppExcel.Range(AppExcel.Selection, AppExcel.Selection.End(xlDown)).Select
AppExcel.Selection.ClearContents

'I thought the following would be equivalent to the above lines - the middle line Fails on error 'Object variable or With block variable not set

With mysheet
                   
   .Range("A2").Select
   .Range(Selection, Selection.End(xlDown)).Select     'Fails on error 'Object variable or With block variable not set 
   .Cells.ClearContents
           
End With

If you look at Selection in VBA help you will see that it is part of the Application or Window objects. It is not qualified in your second example, whereas it is within the Application object in the first.

To further Bob's answer, it is rarely necessary or desirable to explicitly select objects in Excel prior to operating on them. I would suggest rewriting your code to the following equivalent:

mysheet.Range(mysheet.Range("A2"), mysheet.Range("A2").End(xlDown)).ClearContents

 Thanks to you both for your help.  The suggestion works perfectly and the methodology is beginning to gel (I hope!). 

The other thing to think about here is if you have blanks in your data or any type of non-contiguous data structure.  If this is a possibility for you, the xldown may not be the right option for you, but rather go from the bottom up to find the last cell and keep your dynamic range.  If this is the case, you could use a simple change...

mysheet.Range(mysheet.Range("A2"), mysheet.Range("A" & mysheet.Rows.Count).End(xlUp)).ClearContents