Problem with Insert statement?

CREATE TABLE [TransOverride] (
      [Policy_Nbr] [varchar] (7) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL ,
      [Trans_CodeOrig] [varchar] (6) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL ,
      [Trans_Eff_Date] [datetime] NOT NULL ,
      [Override_Code] [varchar] (2) COLLATE SQL_Latin1_General_CP1_CI_AS NULL ,
      [NR_CodeOvr] [varchar] (1) COLLATE SQL_Latin1_General_CP1_CI_AS NULL ,
      [Trans_CodeOvr] [varchar] (6) COLLATE SQL_Latin1_General_CP1_CI_AS NULL ,
      [CreatedDate] [datetime] NOT NULL CONSTRAINT [DF__TransOver__Creat__70A8B9AE] DEFAULT (getdate()),
      [CreatedUID] [nvarchar] (48) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL ,
      [ModifiedDate] [datetime] NOT NULL CONSTRAINT [DF__TransOver__Modif__719CDDE7] DEFAULT (getdate()),
      [ModifiedUID] [nvarchar] (48) COLLATE SQL_Latin1_General_CP1_CI_AS NULL ,
      [Plan_Year] [int] NOT NULL CONSTRAINT [DF__TransOver__Plan___56757D0D] DEFAULT (2004),
      CONSTRAINT [cnTransOverride_PK] PRIMARY KEY  CLUSTERED
      (
            [Policy_Nbr],
            [Trans_CodeOrig],
            [Trans_Eff_Date]
      )  ON [PRIMARY] ,
      CONSTRAINT [cnTransOverride_NR_CodeOvr_CK] CHECK ([NR_CodeOvr] = '' or ([NR_CodeOvr] = 'R' or [NR_CodeOvr] = 'N')),
      CONSTRAINT [cnTransOverride_Override_Code_CK] CHECK ([Override_Code] = '' or ([Override_Code] = 'OT' or ([Override_Code] = 'AU' or ([Override_Code] = 'MS' or ([Override_Code] = 'EN' or ([Override_Code] = 'AO' or [Override_Code] = 'AC'))))))
) ON [PRIMARY]
GO


This is my table however I only want to insert several attributes.

 strsql = "UPDATE [CCFinSol].[dbo].[TransOverride] SET " & "Policy_Nbr='" & txtPolicyNumber.Text & "',Trans_CodeOrig='" & cmbOriginalTransCode.Text & "', Trans_Eff_Date='" & DateEditTransEff.Value & "', Override_Code='" & cmbOverrideAction.Text & "', NR_CodeOvr='" & cmbOverrideNR.Text & "', Trans_CodeOvr='" & cmbOverrideTransactionCode.Text & "', Plan_Year='" & txtPlanYear.Text & "'"
           

System.Data.SqlClient.SqlException: Violation of Primary Key constrait 'cnTransOveride_PK'.
Cannot insert duplicate key in object 'TransOveride'. The statement has been terminated.
at System.Data.SqlClient.SqlCommand.ExecuteNonQuery() at CCTransOverride.EditForm.DoSave() in
C:\Documents and Settings\mcupryk\My Documents\Visual Studio Projects\CCFinSol\CCTransOverride\EditForm.vb:line 515

What should I do?