Webhook Iteration Count?

Is there any way to keep track of the number of iterations when running a repeat section in a webhook? I have a number of records that can be added with a grid edit so there may be multiple records created at once. When they are created, I am trying to create a webhook that will give each a different number in a particular field but the numbers cannot be unique to the table because the records are child to a parent table and the numbers for each child belonging to a parent will be independent of children belonging to other parent records. As an example, if a user added two records in grid edit, one needs a "1" in the field and the second needs a "2" in the field. If I can track iteration numbers in a webhook repeat, then this would be simple but I cannot figure out how to do so. If I cannot do that, any suggestions? Thanks!