hi Paul,
you're better off not converting the field itself but converting your parameter (assuming that you've got a parameter to enter the date) to match the field.
e.g.
{yourdatefield} = totext({?yourdateparam},'dd/MM/yy')
the reason is that if you try to convert the field itself, then that will not be processed at the database end. performance will then suffer. you can verify what's being processing in the Database menu > Show SQL Query.
-jamie