System Target File Pushbutton

When creating a System Target File, I would like to have a push button that then opens a folder browser window. On selecting the relevant folder, it should return and populate a text box with the folder path.

I have found that a pushbutton type may be implemented but can find no other documentation for it. Maybe someone can enlighten me. The reference documentation I have found for this is:

http://www.mathworks.co.uk/help/rtw/ug/customizing-system-target-files.html#bp6dmru