changing Excel test values between tests

I'm using SoapUI Pro 4.5.2; I've got simple data in an excel spreadsheet that is getting used by a test loop, so far so good.  But often, after I've run a test in SoapUI, if I change data in the spreadsheet and attempt to save it, Excel says it cannot due to a sharing violation, forces change to another spreadsheet, etc., etc.  Very messy.  Sometime later, due to passage of time or attempts to close it or whatever, it straightens itself out, but it's aggravating (because I can't tell when it's ok to save).

Is there some way in SoapUI to 'close' use of the Excel file, so that it is free to be changed by Excel between tests.

I've tried closing Excel before running the test, then running the test, then opening it in Excel again, but have the same problem -- I cannot save it. 

Anyone know a good way to do this?  I'd really rather not have to close SoapUI between each test.