Trouble with setting up Transaction/Stored Procedure

Being relatively new to both SQL and the concept of transaction I am having some troubles with the following scenario:
 
I have a database named Event2 that contains two tables.

The first table Events is where the information for each event is stored.  The table consists of:

ID(primary key)      int                  
Date                  smalldatetime      
Time                  varchar(50)      
Location            varchar(50)      
Number            int      
Name                  varchar(50)      
Description            varchar(50)

The second table Attendees is where in the information is stored for each person who signs up for an event.  The table consists of:

PersonID(primary key)      int      
FirstName                  varchar(50)      
LastName                  varchar(50)      
PhoneNumber                  varchar(50)      
Email                        varchar(50)      
Event                        int

Each row in the Attendees table is associated with an event that is listed in the Events table. The value in the Event column of the Attendees table displays the ID of the event it is associated with in the Events table.

Furthermore, it is important to note that the Number column in the Events table displays the number of rows that exist (were created) in the Attendees table for that specific event (each row in the Attendees table represents a seat at an event).

It may also be interesting to note that every column in each of the talbles allows nulls (with the exception of the primary keys).

This brings me to my problem.  I am working on a stored procedure that will make any changes an administrator makes to a specific event (including the total number of seats at the event, keeping mind to never delete a person/seat who has already signed up for an event).

Here is what I have so far  (it doesnt work).


SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

CREATE PROCEDURE [dbo].[UpdateEvent2]
@Date smalldatetime,
@Time varchar (50),
@Name varchar (50),
@Description varchar (50),
@WebTotalSeats varchar (50),
@ID int

AS

BEGIN TRANSACTION

UPDATE Events
SET
Date = @Date,
Time = @Time,
Name = @Name,
Description = @Description
WHERE ID = @ID

SELECT Number AS DBTotalSeats FROM Events WHERE ID = @ID

IF @WebTotalSeats = DBTotalSeats

COMMIT TRANSACTION

 


ELSE
IF @WebTotalSeats < DBTotalSeats

SELECT DBTotalSeats - @WebTotalSeats As DecreaseDifference

UPDATE Events  
SET
Number = @WebTotalSeats
WHERE ID = @ID

IF @@ROWCOUNT = 1

DELETE Top DecreaseDifference
FROM Attendees
WHERE Event = @ID AND FirstName IS NULL

IF @@ROWCOUNT <> DecreaseDifference
ROLLBACK TRANSACTION
ELSE
COMMIT TRANSACTION
END




ELSE
IF @WebTotalSeats > DBTotalSeats
SELECT @WebTotalSeats - DBTotalSeats As IncreaseDifference

UPDATE Events
SET
Number = @WebTotalSeats
WHERE ID = @ID

IF @@ROWCOUNT = 1

INSERT Top IncreaseDifference
INTO Attendees (Event)
VALUES (@WebTotalSeats)
 
IF @@ROWCOUNT <> IncreaseDifference
ROLLBACK TRANSACTION
ELSE
COMMIT TRANSACTION