Read from Excel datasource cell is integer instead of text

I'm using Soap UI PRO 4.5.1 I'm trying to read from Excel datasource to use in my Assertions Xpath Expression section (top half of the Assertions window in the XPath Match), something like string(${DataSource2#test}), where test is the column name and DataSource2 is the Excel spreadsheet, the values in the column test are ab-cd, where ab and cd are integers, I want it to show up in the Xpath Expression exactly the way it is, for example "12-02" I wanted it to stay as "12-02" instead I get "10" because it thinks that the dash "-" is a subtraction operation and it's doing 12-02=10. I've formatted the entire sheet in Excel as Text, that didn't seem to help, and also convert the value to a string, can some one help?

Thanks,
Hao