declare @max int , @cnt int
declare @t table (id int ,Company varchar(50),Site nvarchar(20),TransDate Datetime) 
set @cnt =1 
--select * from #TransDetail
select @max = MAX(Number)  from #TransDetail
while ( @max > = @cnt)
	begin 
	insert into @t  select @cnt, 'COMP','MyCompany','2012-12-01 00:00:00'
	insert into @t  select @cnt, 'COMPUSA','MyNewCompany','2012-12-02 00:00:00'
	set @cnt = @cnt + 1 
	end 

select 
     a.*
from #TransDetail b 
right join @t a
on a.id = b.number and  a.Company = b.Company
where b.number is null

;WITH MassagedData AS (
	SELECT Company, 
		MIN_Number = MIN(Number), 
		MAX_Number = MAX(Number),
		rn = ROW_NUMBER() OVER(PARTITION BY Company ORDER BY MIN(Number))
	FROM (
		SELECT Company, Number,
			gp = Number - ROW_NUMBER() OVER(PARTITION BY Company ORDER BY Number) 
		FROM #TransDetail
	) d
	GROUP BY Company, gp
)
SELECT a.Company, PriorNumber = a.MAX_Number, NextNumber = b.MIN_Number
INTO #RangeBoundaries
FROM MassagedData a
INNER JOIN MassagedData b 
	ON b.Company = a.Company AND b.rn = a.rn + 1

SELECT r.Company, p.[Site], 
	r.PriorNumber, PriorDate = p.TransDate, PriorTime = p.TransTime, 
	r.NextNumber, NextDate = n.TransDate, NextTime = n.TransTime 
FROM #RangeBoundaries r
LEFT JOIN #TransDetail p ON p.Company = r.Company AND p.Number = r.PriorNumber
LEFT JOIN #TransDetail n ON n.Company = r.Company AND n.Number = r.NextNumber
ORDER BY r.Company, r.PriorNumber

;
WITH Tally (n) AS (
    SELECT TOP (SELECT MAX(Number) FROM #TransDetail) 
        ROW_NUMBER() OVER (ORDER BY (SELECT NULL))
    FROM sys.all_columns), 
    IntialGrouping AS (
    SELECT Site, Company, TransDate, TransTime, StartNumber=MIN(Number), EndNumber=MAX(Number)
    FROM (
        SELECT ID, Number, TransDate, TransTime, Site, Company
            ,rn=Number-ROW_NUMBER() OVER (PARTITION BY TransDate, Site, Company ORDER BY Number)
        FROM #TransDetail) a
    GROUP BY TransDate,TransTime,Site,Company,rn)
SELECT Site, Company, TransDate, TransTime, Number=n
FROM (
    SELECT Site, Company, TransDate, TransTime, StartNumber=MIN(Number), EndNumber=MAX(Number)
    FROM (
        SELECT Site, Company, TransDate, TransTime, Number, rn
        FROM (
            SELECT Site, Company, TransDate, TransTime, Number
                ,rn=ROW_NUMBER() OVER (PARTITION BY TransDate, Site, Company ORDER BY Number)/2
            FROM IntialGrouping a
            CROSS APPLY (VALUES (StartNumber-1),(EndNumber+1)) b(Number)
        ) a
    ) a
    GROUP BY Site, Company, TransDate, TransTime, rn
    HAVING COUNT(*) = 2) a
CROSS APPLY (SELECT n FROM Tally WHERE n BETWEEN StartNumber AND EndNumber) b;