User Default Column Value In INSERT Stored Procedure

From my ASP.NET application I am calling an INSERT stored procedure, there is a default value for one of the columns in the table that the INSERT procedure places the data into. How do I specify that I want the default value to be used instead? (Or do I have to specify the actual default value in my parameters)

SITUATIONAL TABLE:
Column 1: int
Column 2: string
Column 3: int default -1
SITUATIONAL STORED PROCEDURE
INSERT INTO TABLE
(Column 1, Column 2, Column 3)
VALUES
(?, ?, ?)
SITUATIONAL ASP.NET CODE
create paramter (Column 1, 12)
if (x = 0)
{create parameter (Column 2, "test")}
else
{
create parameter (Column 3, 24)
create parameter (Column 2, DBNull.Value)
}