Oh My I cannot figure this out, HELP!

Can anyone tell me why this would not work?
IntervalType = "Shift"

CREATE Procedure UpdateScheduleInterval
@IntervalType char (5),
@IntervalName varchar (20),
@StartTime datetime,
@EndTime datetime

AS
DECLARE @RetCode int
DECLARE @_error int
DECLARE @_rowcount int
Declare @ErrorMsg char (50)
Declare @BeginTime datetime
Declare @ExpireTime datetime
Declare @BeginInt int
Declare @ExpireInt int
Select @BeginTime = @StartTime
Select @ExpireTime = @EndTime
Select @BeginInt = datepart(mi, @BeginTime) + datepart(hh, @Begintime) * 60
Select @ExpireInt = datepart(mi, @ExpireTime) + datepart(hh, @ExpireTime) * 60

SELECT @errorMsg = 'UpdateScheduleInterval could not Update ' + @IntervalType
SELECT @RetCode = 0
BEGIN TRAN

If @IntervalType = "Shift"
Begin
UPDATE ScheduleDefine
SET
ShiftInterval = @IntervalName
where (datepart(mi, starttime)+ datepart(hh, starttime) * 60) >= @beginInt and (datepart(mi, starttime)+ datepart(hh, starttime) * 60) <= @Expireint
end