Getting Max Date From List

I'm using the following code (borrowed from another site) to output the DateLastModified of 4 log files to cells A1:A4:

Function FileLastModified(strFullFileName As String)
Dim fs As Object, f As Object, s As String
Set fs = CreateObject("Scripting.FileSystemObject")
Set f = fs.GetFile(strFullFileName)
s = vbCrLf & f.DateLastModified

[Code] .....

The issue I'm having is that the output from the above seems to contain a large number of proceeding spaces. These can be removed with the Clean Function, leaving me with 4 resulting cells A5:A8 which look like this, and are correct:

03/06/2012 14:32:59
02/06/2012 23:27:31
01/06/2012 01:23:20
03/06/2012 12:46:17

What I want to do is use the MAX function to return the latest date and time from the list of 4 into cell A10. This doesn't seem to be working, from what I have read looking at other sites this is because the data may be in the wrong format, though I'm not sure how as the cells are formatted to the correct custom format dd/mm/yy hh/mm/ss, changing the format of this cell hasn't worked either.