As per the requirement what i understood, here is the code: you need to manipulate it somewhat as per your convinience:

Declare @count INT

DECLARE @finalOutput VARCHAR(30)

DECLARE @dotCount INT

DECLARE @result VARCHAR(40)

SET @dotCount = 1

SET @finalOutput = ''

SET @result = ''

SET @count = 0

WHILE @count <= LEN('123456789123')/3

BEGIN

IF @count = LEN('123456789123')/3

BEGIN

SET @finalOutput = SUBSTRING('123456789123',@dotCount,3)

END

ELSE

BEGIN

SET @finalOutput = SUBSTRING('123456789123',@dotCount,3) + '.'

END

SET @result = @result + @finalOutput

SET @dotCount = @dotCount + 3

SET @count = @count + 1

END

SET @result = SUBSTRING(@result, 1,LEN(@result) - 1)

PRINT (@result)