I have created a merge module to handle my database installation.  The
merge module includes some custom UI components to gather Database
information.  I have then include the merge a in my main nstaller.wsx
file and the mergeref tag is included inside a feature tag. The main
installer.wsx file  use the wixui_featuretree ui. When the installer
runs the UI for my merge module fires first and then the other custom
ui's fire. I only want the module  UI to fire once the feature in
select  from the feature tree.