Andy,
Here is a link to an application note. The note is about customizing controls and indicators. Once created, you can put the control in the user.lib directory and the next time you start labview, the new control will be available.
http://digital.ni.com/appnotes.nsf/b0be082ea11554328625648f006a132a/b26a96829c91d7e9862568b6007be825?OpenDocument
If the link does not work put "custom controls app note" in the search box on NI's website and its the first link.
Jared