Adding Javascript to Dashboards

Adding Javascript to Dashboards

I have hit a brick wall and I seem to need Javascript, but can't see how I can get it to work.

I want to try and overcome the limitation of the dashboard feature that you can't filter all reports in a dashboard from a single filter option. I need this function.

I looked at adding a form on my HTML page which adds in the appropriate CRITERIA code into a URL 
like so ... &ZOHO_CRITERIA="YearMonth"='201005'

But this won't work as the Dashboard is inside an IFRAME. 

I realised I could add my form into the Dashboard itself using the Add Text feature in the Dashboard Edit View. I created some simple forms that would generate the  &ZOHO_CRITERIA="YearMonth"='xxxxxx' options I needed.

However when I ran this, selected an option the new option page failed to render as the new URL was missing the "OBJID=xxxxxx&STANDALONE=true&ZDB_THEME_NAME=blue" part.

So I re-edited my form to output the entire string into the URL on selection, like this ...
OBJID=xxxxxx&STANDALONE=true&ZDB_THEME_NAME=blue&ZOHO_CRITERIA="YearMonth"='201005'

But this did not work either. The problem is that the form data is URL ENCODED and so the resultant URL fails as it is like this ...
https ://reports.zoho.com/ZDBDataSheetView.cc?OBJID%xxxxxxx&STANDALONE=true&ZDB_THEME_NAME=blue&YearMonth=05

Now I am totally stuck. I can't seem to use Javascript forms. All Javascript I add is ignored. I have no way to URL enencode, or to deliver a valid URL. I am stuck with a Dashboard system that has a severe limitation.