Sorting data

Hi,

I am trying to sort some data within my worksheet.

There are headings in rows 1, columns A to J.
I would like to sort data in ascending order for (in ascending order): column C then
column D.

My code is below:
Selection.CurrentRegion.Select
Selection.sort key3:=Range("c1"), order3:=xlAscending, key4:=Range("d1"), order4:=xlAscending, Header:=xlGuess, ordercustom:=1

When I run this I get an error: run time error '1004'.
"Application-defined or object-defined run time error"

Thanks for any advice!

Mimi