I think the easiest and fast way is to use conditional show expression on layout tab, to show th CH101 when the particular project is selected.
The drawback is that it will work for the selection of project field whether it's done in CH100 or some other way.
Nevertheless you can organize the sheets so that it will be more natural for the user.
Suppose that the field is named [Project Name]
=not isnull(Only([Project Name]))
The first one works with explicit selections.
The second one works even if some other field selections lead to the only one possible project.
You'd better post your attempts, It helps to get the context.