how to Check data after Insert Trigger

Hi friends,

I need to insert data from one database table to another database table by after Insert trigger. Now

I need to check whether that another database table already have the data or not. If there already have the data then do some exception but not show error.

CREATE TRIGGER [dbo].[TRIG_TABLE1] 
ON [dbo].[Table1] AFTER INSERT AS
BEGIN
    INSERT INTO Table2(CustID,DateCreated,DateModify)
    SELECT CustID, DateCreated, DateModify
    FROM INSERTED
END

I have done this far but can not check whether the table already have the data or not. Please solve this problem.

Thanks  in advance.