To use a paragraph format to force a jump from contents or index to a secondary window, assign property Window to the format of the paragraph that is the target of the contents or index entry (not to the paragraph format of the entry itself):
A jump from the contents loads a topic in a secondary window only if the first paragraph in the topic has a format assigned the Window property. However, a Window marker in the first paragraph overrides any Window property assigned to that paragraph format.
A jump from the index loads the topic in a secondary window if the Window paragraph format appears anywhere in the topic. For paragraphs after the first in a topic, whichever comes first, Window marker or paragraph assigned the Window property, determines which secondary window will be used for jumps from the index.
> 8 Generating Microsoft HTML Help > 8.7 Using secondary windows in HTML Help > 8.7.3 Jumping from contents or index to a secondary window > 18.104.22.168 Assigning a secondary window with a paragraph format