We want the ability to incrementally partially allocate or generate tasks for a movement request

Summary:

We need to execute below 2 scenarios:

1. Movement request with req qty of 100 with entire stock available in WMS. Allocate full but generate tasks only for 20 qty initially. Then in next run generate tasks for the next 20 qty and so on and so forth till entire Req qty is completed.
2. Movement request with req qty of 100 with entire stock available in WMS. Allocate only for 20 qty initially with tasks generated for the same. Then in next run allocate next 20 qty with task generation and so on and so forth till entire Req qty is completed.

also is there a selection rule available on the task to decide how much of the allocations need to be converted to task.