Hi pajamaham and welcome to the RH community.
To be honest I don't think you can do this with the method you are using. Popups were never designed to work that way. Perhaps a workaround would be to display the popup information in a new window. Not exactly elegant but it would do what you want.
Thank you, Colum.
I thought about doing that but I was hoping that someone may have a simple solution. Thanks again!
On my system (RH22.214.171.124, Windows XP, HTML Help (CHM) output) I can scroll a popup with the vertical scrollbar but not with the mouse wheel. When I use KatMouse both scrollbars and mouse wheel work.
In the preview window (eyeglasses icon) both scrollbars and mouse wheel work.
The call I use is:
which I make with Insert > Hyperlink, Display in auto-sizing popup.