Can a formula field be converted to read only after a condition is met?

Thanks, this is definitely educational and new information for us, but we are working with a formula numeric field within on table and the snapshot feature doesn't exist for this field type unless I'm missing something. Also within our formula numeric field, there aren't any lookup fields that we could utilize snapshot for that would solve our problem.

Is there a different solution for a formula numeric field, where we are plugging in specific numeric values based on other lookup fields?