if you don't have any graphs on your dashboard, click on the printer friendly icon on the bottom left corner and select HTML, & now Save the page with .xls extension.
don't know of any other direct solution :-(
I want to say no you can't. I'm trying to imagine what you are trying to do which is to have one button that will nicely download multiple reports from a dashboard page into Excel, only downloading the reports, and nothing else. Well, that can't be done out-of-the-box and you definitely can't change the "download" link to do this.
Now, having said that, I'll give you several ways you can do this. None are pretty though.
1) Click anywhere in your dashboard and press CNTRL-A, then CNTRL-C. This will highlight the whole dashboard and copy it to the clipboard. You can then paste it in Excel.
2) Click on the Print>HTML. When the page renders, save it as MHTML. Then open the file in Excel. Save it as an Excel file.
3) Third Way
a) Open the dashboard to the page you wish to "copy."
b) Highlight the address you see in the address bar and copy it to the clipboard.
c) Now open up Excel and click on the "Get External Data from Web" button. (I am using Excel 2007 for this example and you can find this command by searching through the commands.)
d) Paste the URL in the window that appears. Scroll to the end and add &Format=Excel.
e) Click the "Go" button. The OBI login window will appear.
f) Log in to OBI in the usual manner.
g) The dashboard page will appear in the window along with many yellow arrows, each referring to an element on the page. Select the yellow arrow corresponding to the dashboard page itself.
h) Click the "Import" button. The dashboard page will import into Excel.
I tried all the options none of them are working as per the expectation. We had a discussion with oracle technical team also but they said this option is not available yet. They said they are targeting to implement this feature in the coming release 184.108.40.206.0.