Could not find stored procedure 'sp_start_job'

I'm trying to run a ms sql server agent job from within my vb.net code using sp_start_job and getting exception...

Could not find stored procedure 'sp_start_job'.

... so obviously I'm doing something wrong.  My vb code contains is ...

        jobCommand = New SqlCommand("sp_start_job", sqlConn)
        jobCommand.CommandType = CommandType.StoredProcedure
        jobParameter = New SqlParameter("@job_name", SqlDbType.VarChar)
        jobParameter.Direction = ParameterDirection.Input
        jobCommand.Parameters.Add(jobParameter)
        jobParameter.Value = "nameOfServerAgentJob"
        jobCommand.ExecuteNonQuery()

Can someone show me how to run the SQL Server Agent job properly from my vb code?

Thanks tonnes for any help, Roscoe