Yes, you should be able to use the Excel_RangeSetitem to send a string to the Excel table. Look at the ExcelDemo (see link) they send data to Excel two ways first using RangeSetitem to send data one at a time, then it shows sending an entire array using safearray. Look up on the Microsoft website for more information about using this function with different datatypes or in CVI click on Help on the function panel of Excel_RangeSetitem to see if help is provided by your Excel Server to see more about sending different datatypes using that function.
http://zone.ni.com/devzone/explprog.nsf/6c163603265406328625682a006ed37d/97383d950b2b38fe862568940057d3b4?OpenDocument
Joji