Within SSRS reports, you may sometimes want to show more details for a given record but don’t necessarily want to add it to the existing report or go to another report. Here is a neat solution. You can add JavaScript to your report and have a second report window pop up with the details! Let’s take a look at how we can do this. First you will need to create two reports; your main report and the second report that will show up on the pop up window with details.
On the first report you will need to decide where you want your user to click to pull up the second report. In our example here, we have a reservation list. We will be clicking on the Customer Name to get more details about that customer.

Next, we will go to the text box properties and then the Action tab. Select ‘Go to URL’ and then click on the expression button.

Here is where the magic happens. Using SSRS URL Access, we will send commands to the report server and pull up the second report.

Here is the code we will use for our reports.
="javascript:void window.open(" &"'"& Globals!ReportServerUrl &"/Pages/ReportViewer.aspx?"
&Globals!ReportFolder &"/Customer+Details&rc:Parameters=False
&CustomerID="& Fields!CustomerID.Value &"
','CustomerDetailsWindow','left=370,top=180,width=940,height=300,status=no,menubar=no,scrollbars=no,location=yes'" & ")"
The first line uses a global variable to populate the report server URL and report viewer. The second line puts in a report folder value, and specifies a report name. Our pop up report is called ‘Customer Details.rdl’, but as you can see here we just specify the report name without the .rdl at the end. We will also pass in a parameter option of ‘Parameters=False’ on the second line. This will turn off the parameter drop down box on the controls. We don’t want our report to give the option of selecting a different customer. If you need to pass more than one parameter, simply copy the third line and paste the copy below line three and modify with the new parameter values. In our example, the third line specifies the parameter name (CustomerID) on the second report, and the value from the main report. For this report, we will be passing in (Fields!CustomerID.Value). Finally, on the last line we specify some additional properties that we want the pop up window to have such as the width and height.
We only use one URL parameter value (Parameters=False) in our example. However, there are quite a few more that can help customize your secondary report window. To find more information about parameter values, follow this link:
If you are having a hard time getting your report to work, I suggest first going to your report server URL (http://YourServer/reportserver), browse to your report and try setting your SSRS parameter strings to make sure you have the correct syntax. You should then be able to pull it apart and insert it into your JavaScript expression.
Here is a screenshot of our final solution. When we click on the Customer Name, we get a second report with additional customer information.

More information on using SSRS URL Access can be found here:
http://msdn.microsoft.com/en-us/library/ms153586