From your description above this could be a solution.
DECLARE @T TABLE (AttemptDiff TIME)
DECLARE @FirstTry DATETIME,
SET @FirstTry = GETDATE()
WAITFOR DELAY '00:00:05'
SET @SecondTry = GETDATE()
SET @DiffSeconds = DATEDIFF(SECOND, @FirstTry, @SecondTry)
SET @FirstTry = DATEADD(second, @DiffSeconds, @FirstTry)
INSERT INTO @T
SELECT CONVERT(VARCHAR, @FirstTry, 108)
SELECT * FROM @T t
This solution could work fro SQL Server 2012 for other version keep the time as varchar.