Hi Martin
See the comments in the xsp.properties.sample file located in the properties folder under the your Domino data directory.
I have copy/pasted them here, as follows:
# #######################################
# CLIENT SIDE JAVASCRIPT
# #######################################
# The version of the Dojo Toolkit to use.
# By default the Dojo version is detected by examining the folder
# Data/domino/js/ for subfolders with names like dojo-,
# and using the latest version available.
# Change this setting if you are installing different versions of Dojo
# in that folder and you need XPages to use a specific version.
# Note, using XPages with a Dojo version other than the default is unsupported;
# if you do so you will need to test for compatibility problems.
#xsp.client.script.dojo.version=
So if you install Dojo 1.6 on the server it will get picked up by all apps at this is the greatest verstion number.
You probably don't want to apply Dojo 1.6 to all XPages apps, so you could set the general Dojo version to 1.5.0 - as described above:
xsp.client.script.dojo.version=1.5.0
Then for a particular app, you could set the Dojo version to 1.6.0 in the application's xsp.properties file in Domino Designer.
This is assuming that you only want to use Dojo 1.6 with experimental apps, as there could well be other issues when it is integrated with XPages on the fly like this. Generally we have issues to resolve whenever we upgrade to a new version of Dojo, so I expect your experience to be no different.
Hope this answers your question,
-Martin