Macro issue in XL03 "Compatability Mode"

[Ray]

Hi -

Using XL07 in Compatability Mode, I've created what I *thought* was a
relatively simple procedure to sort a range based on a user-selected
cell. For example, if user clicks on cell D3, the range A4:Z50 is
sorted based on values in column D.

The procedure ran fine on my computer, but when a native XL03 user
clicks on a 'header' (in row 3), the procedure throws an error:
Compile Error: Variable Not Defined
with SortOn:=xlSortOnValues highlighted as the error.

The whole line is:
ActiveWorkbook.Worksheets("Exec Summary").Sort.SortFields.Add
Key:=Range( _
"K5:K41"), SortOn:=xlSortOnValues, Order:=xlAscending,
DataOption:= _
xlSortNormal

Is 'xlSortOnValues' referencing an Object Library that's not available
by Default? Can I programmatically check for it (on the user's
machine) and activate if not already available?

Any help is greatly appreciated!

Thanks, ray