mdfind piped to automator?
As a test I created an Automator app that just copies finder items to a directory.  "Copy Finder Items" Action

And then used

theFind=`mdfind -onlyin . 'kMDItemContentType == com.microsoft.excel.xls'`;automator -i "$theFind"  /Users/UserName/Desktop/testF/test2.app


The backpicks  "`"  insure that the first commands result is placed in the variable theFind and then we can pass theFind onto the next command by calling it with "$theFind".  The quotes around it also in sure any text passed on is quoted.

The Automator app is then passed an Alias list. 


  {alias "hard drive:Users:Username:Dropbox:Kit:Unit2.xls", alias "hard
  drive:Users:Username:Dropbox:Kit:Unit3.xls"}


So depending on you other actions you may need to convert them to POSIX paths.


  {"/Users/Username/Dropbox/Kit/Unit2.xls", "/Users/Username/Dropbox/Kit/Unit3.xls"}