PL/SQL:set output value with reflection

I have the following stored procedure:

Procedure MyProc
(
Output1 OUT VARCHAR2
Output2 OUT VARCHAR2
Output3 OUT VARCHAR2
)
IS
BEGIN
SELECT mt.value
from myTable mt
join all_arguments aa on aa.argument_name=mt.key;
END myProc;

How can I put mt.Value into the corresponding argument (i.e. Output1, output2, or output3?)