Find the jnlp resource of the diy you want to update.

Go to http://rails.dev.concord.org/application-info/
Find the diy url in the first column of the table.
Find the SDS URL and SDS JNLP in the last column of the table
Combine them like this:
SDS URL/jnlp/SDS JNLP
If you go to that address you'll see a web page for the jnlp resource for the diy.

Here is an example url: http://saildataservice.concord.org/8/jnlp/273
That is the jnlp resource for the ccdiy

Figure out the new url for the jnlp

On the jnlp resource web page is a Url: for the actual jnlp file.
From the example above this url is: http://jnlp.concord.org/dev/org/concord/maven-jnlp/all-otrunk-snapshot/all-otrunk-snapshot.jnlp

To see other available versions of that jnlp look at the directory that jnlp file is in.
So from the example above look at: http://jnlp.concord.org/dev/org/concord/maven-jnlp/all-otrunk-snapshot/

All jnlp that end with a timestamps do not change. For example:
all-otrunk-snapshot-0.1.0-20080111.153223.jnlp

These are in effect frozen. jnlps that don't end in a timestamp will get updated each time the jnlp project is build on continuum. For example:
all-otrunk-snapshot.jnlp

Update the jnlp resource

Back on the jnlp resource page of the sds, click the edit link.
Change the url field in form an click save.

Updating just a few jars in a jnlp

The only way to do this right now is to make a custom jnlp. Here is how it is done:
ssh maven@jnlp.concord.org
cd /var/tomcat/jnlp_tomcat/webapps/dev/org/concord/maven-jnlp/capa-otrunk
cp capa-otrunk-0.1.0-20080215.201427.jnlp capa-otrunk-0.1.0-20080215.201427-custom.jnlp

edit capa-otrunk-0.1.0-20080215.201427-custom.jnlp so it has a reference to the version of the jars needed.
update the sds jnlp like you do to freeze the jar so it points to the -custom.jnlp url.