Hi Françoise,
If you are able to switch to a CustomSQL statement you may be able to specify the range as part of the table name:
New SQL Query(
Connection( New Data Connector( ID( "demo_excel" ) ) ),
QueryName( "Sheet1$" ),
CustomSQL( "SELECT * FROM [Sheet1$A3:XFD] t1;" ) // Select from cells after A3 and all columns
) << Run;