Unfortunately, SQL Server does not understand those nice little shortcuts that we all picked up from other languages ( the ones I miss the most are "++" and "--" ). Try, this it should work for you. Also, remember, any value added, subtracted, mutliplied etc.... to a null value will end up as null.
DECLARE @test varchar( 20 )
DECLARE @inx int
SELECT @test = 'A'
SELECT @inx = 0
WHILE( @inx <= 5 )
BEGIN
SELECT @test = @test + 'B'
SELECT @inx = @inx + 1
SELECT @test
END
jimmY