Keyed Array Data Structure %LOOKUPLT

[Dave <dfx1@xxxxxxxxxxxxxx>]

Hi,

I have this lookup problem. Can't believe it.
IBM reference says : A "Keyed Array Data Structure" is an array data
structure with one subfield
identified as the search or sort key.

I don't see how to identify one subfield as the search or sort key or where
this is explained.

This compiles :
$I = %LOOKUP ( myDate : myArray(*).DATE )

This doesn't
 $I = %LOOKUPLT ( myDate : myArray(*).DATE )

My Array DS :

D myArray            DS                  DIM(10) QUALIFIED
D  CODE                               LIKE(refcode)
D  DATE                               LIKE(refdate)

Thanks