The only way I know of doing this:
doc.SendStringToExecute("._-opensheetset " + yourSheetSetFilePath + "\n", false, false, true);
... And this will either open and set the target sheet set current (
if not already open), or set the target sheet set current (
if already open).
You may need to hook the CommandEnded event, filtering for OpenSheetSet Command of course, in order to resume your code (
once the target sheet set has been made current), but something along this line should work for you, no?
HTH