Trigger context by filter value?
With Drupal there are so many way to do things - here is one way to achieve what you need:


Go to admin/blocks and add your block to the region you want it to show up in, then set it to display on only the page for that view
In your theme css hide that block (display:none)
Add some javascript to display the block and bind it to the onchange event for the value you want, either add the js in your module or your theme.


I have not gone into specifics as each step can have variations on how you would like to implement them, but the above is one potential solution to the problem

Using context could work if you submit the view filter to a different path and then set a context to show the block on that path, but if you wnat to do it via an onChange its easier using Js &amp; Css.

Modules that may also help:


http://drupal.org/project/views_hacks
http://drupal.org/project/views_dependent_filters