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While possible, this would involve a LOT of work and effort. Because you are talking about 2 different documents, you are dealing with two sets of DOMs (Document Object Models).
In theory, you would need to identify the point at which the spill-ver (into the other frame) would occur and then trigger another layer to show in that (right) frame. There would be quite a bit of scripting involved in this - and to be honest, I think that it would be more trouble that the outcome would be worth...
HTH