I don't recommend this approach, but you can structure a WHILE loop to act as a DO...UNTIL loop.
WHILE (1 = 1)
BEGIN
--do stuff
.....
-- do more stuff
if (break_condition = true)
BREAK
END
That said - from what you're describing you'd be better off bulk loading to some staging table, and doing your validation there before moving it to the permanent home.....
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Your lack of planning does not constitute an emergency on my part...unless you're my manager...or a director and above...or a really loud-spoken end-user..All right - what was my emergency again?