Hi, using your help I come up with the following solution for the trigger:

IF (@action = 'INSERT')

BEGIN

-- update existing balances

UPDATE dbo.AccountBalance

SET Balance = Balance + i.Debit - i.Credit

FROM AccountBalance b,...

Thank you for your help, here is my script:

Stored Procedure:

ALTER PROC [dbo].[usp_UpdateAccountBalance] @AccountId INT, @Amount MONEY

AS

DECLARE @Count INT;

SELECT @Count = COUNT(*) FROM dbo.AccountBalance

WHERE AccountId = @AccountId;

IF (@Count = 0)

BEGIN

INSERT INTO...