alternate with something
1. [for someone] to serve as a substitute for someone. I alternated with Fred as the lead in the school play. They asked Harry to alternate with Ron on the team.
2. [for something] to appear repetitively and regularly in a sequence with something else. (For instance, A alternates with B in the sequence ABABAB.) In this design the straight lines alternate with the circles. The red dots alternate with the blue ones.
See also: alternate