Hello Rj,
In the beaning if you want to pass multiple value to your prompt report make sure you have your drill report has "In list" Insted of "Equal"
Now you need to build the Formula in your excel which should have outcome as 2015;2016....you can build the formula by match , concatenation etc excel functions
Now you do the selection on your Dashboard is in this case 2015 and 2016 if these need to pass into your Drill report then use the following
&lsMEnter_the Years( Enter_the_year is your prompt Text in the drill report)....and then you can Trigger the URL when value changes ( Properties in url button)
eg is something like
http://servername:port//OpenDocument/opendoc/openDocument.jsp?&sIDType=CUID&sWindow=Same-------------etc (various Pramaters you want )
...then &lsMEnter_the Years=( the cell which gives output as 2015;2016)
Hope this helps.....
Thanks
Mayur.P