Dependent requirement

Hi

I am creating a SO , which in turn create a PR through schedule line category.

The PR comes with source (source list maintained ) and the source is another Plant.

The Demand is automatically shown in another plant and it create PR if MRP run happends for that plant.

Our requirement is that the PR should not be shown as Demand to another Plant until the Plant to Plant PO is created.

What will be the solution ?