Are you saying that the only file in the folder will be the one in question - the newest one?
Are there other files?
If that is the only file with the word report, that is an Excel file, you can do the following:
Action: Get files in folder with a file filter of: *report*.xlsx

Action: For Each iterate through the %Files% object created above, store in %file%

Action: Set Variable set %fullname% variable with %file.Fullname%

Then you can launch Excel using that file name.
This only works if it is the only file with "report" that is a .xlsx
But... you can also sort the files on the Get files in folder action by the "Creation time" (created date), descending order. That will give you the most recently created *reports*.xlsx file. Then leave the loop after the first iteration or you access the file with a Set Variable - immediately after the Get files in folder action.
You'd be referencing: %Files[0].fullname%
Which is saying, the first file returned [0] and the fullname property.
Then you don't need the loop. Again, this assumes there are no other *report*.xlsx files that will make their way into the folder.
Hope this help.