Providing A Start And Finish Cell Into A Range

I need to create a range of cells in Column A. I know the first cell, A2. The final occupied cell will vary. Once I have the range object I would like to step through and analyse each cell in turn using a For/Each loop.

The code I have so far is:

Public all_structures As Range 'Range required for for/each loop Column
Public last_structure As Range 'Last cell in Column
Public molcell As Range 'Current cell in range

' Establish range of cells in Column A

Set last_structure = Range("A2").End(xlDown)
Set all_structures = Range(Range("A2"), Range(last_structure)) ***

' Loop through each structure in turn
For Each molcell In all_structures

Loop code In here

Next molcell

When I run I get an error message of "Run-time error '1004': Method 'Range' of object '_Global' failed". It does not like the line marked ***.