Here's an old discussion about some of the issues that exist when exporting to Excel: http://community.tableau.com/ideas/1617
The difficulty is that Tableau is exporting a specific formatting Excel won't recognize the URLs as URLs.
Here are some possibilities to consider:
1. Run a macro after the fact to turn the column you want into URLs.
2. Build the Excel formula for HYPERLINK as a calculated field. It still won't be recognized as a formula by Excel, but you can do what was recommended in the old discussion. Select the rows in the cross-tab (maybe press CTL + A to select the entire cross tab), then copy, then paste into Excel. At that point Excel will recognize the HYPERLINK formula.
I've attached a workbook that demonstrates option #2.
Maybe others will have more ideas for you.
Excel Hyperlink.twbx.zip 8.7 KB
Thanks Joshua, and apologies for not responding sooner, the alert got caught into my spam folder. I did apply the calculation and followed instructions on that post too, but no luck...I know this is an Excel issue so will look for an alternative there though a macro.