I'm not sure what version of CVI you are using, but if you are using CVI 6.0 or greater, the easiest way to communicate with Excel is the Excel Report Tool (excelreport.fp). You can just use the ExcelRpt_WriteData or the ExcelRpt_SetCellValue functions to write strings to cells in Excel. If you don't want to use the excelreport.fp, you would have to put the string in a variant with CA_VariantSetCString and then write the variant to the cell range with Excel_SetProperty on a range object as seen on line 575 of the excel2000demo.prj.
The excelreport.fp tool will save you enormous time in converting datatypes to and from variants and in navigating the huge ActiveX API for Excel. I would use it if you have CVI 6.0 or above.
Best Regards,
Chris Matthew
s
National Instruments