(The image wasn’t there when I started preparing the files)
If you can share a scene file, that would be great. General questions are often more challenging to answer than a file-based question.
Otherwise, I can only offer some guessing, since there are no options by default to make that happen. It is either in the formula itself or animated with a field. Of course, any Xpresso option comes to mind, with MoGraph Selections.
Here are two examples
A formula could work like this
It reads as follow:
If the clone ID is equal to the time (truncated to full numbers), then use the formula, otherwise, ignore it (zero).
All the best