There's SET missing at the beggining of the line. It should be

SET @tempString=@addZero + @tempString

>While looping through a cursor, I'm getting an interger value 600 that I cast to a varchar. The value is really a starting time I am going to use later to append to a date, so I am trying to eventaully make it read '06:00' So I am checking the length and if it = 3, then I want to append the '0' in front. The problem is I'm getting an error message on the line where I add the zero. Without that line I get the print statement to print 600. The error message is:
>