Try something like:

# Order Rows
$tmp = "$mylastcol2".'3';
$Rangea = $Sheet->Range("a1");
$Rangeb = $Sheet->Range("a5");
$Excel->Selection->Sort({Key1 => $Rangea,
                         Order1 => xlDescending,
                         Key2 => $Rangeb});
[download]

Though i never can find much documentation on the sort function, so you may need to play around with it a bit.

edit - also found a sort example:
here