You can do this with a second goal that you connect using Zapier. One of the steps in your zap could check against the cap and enter either a zero or a one.
But.
The second goal will probably get a new datapoint every time that the first goal is updated, so you’ll also need to set an aggregation method of nonzero
So it’s a bit tricky, but possible. As @shanaqui said, there’s a lot of value in taking a manual approach.