DataSource Controls :: Get The Output Parameter From Stored Procedure?

I have stored procedure that increments a number. I am supposed to use the newly generated number and insert it into a table. My question is how do I execute the stored procedure, with a hardcoded value of 3 that it expects as a paramter, receive the number it generates as the output parameter and use it in the insert statement.

Here is the stored procedure code:

CREATE PROCEDURE [dbo].[Generate]
@myid int,
@next_no int output
AS
update mytable
set mynumber=mynumber + 1, @next_no = number
where myid=@myid
RETURN

Here is my insert statement, that I tried and it failed:

EXEC @GetNo = Generate '3'
Insert into customers (custid, name, phone ) values
( @GetNo, 'MSFT', '800-345-5678')