Is this a custom query or OOTB ? if this is a custom query, you will have to create a custom stylesheet,import and assign it to the query. On assignment, it will appear to select when you try to generate a report using report builder.
Hope this helps !!
I can see many stylesheets when i select the Source as the "Office Template".
I have had the Teamcenter Client for Microsoft office feature installed on my 4 Tier RAC's OTW. Guess that's the reason i am able to see these style sheets.
You could import the excelsheet into teamcenter as the excel template and then try selecting it.
Hope this helps !
Save your XSLX template in XSLT format and import the dataset. You should be able to select it.
For more info : http://www.w3schools.com/xsl/xsl_examples.asp