Yes, just create a csv file.
Excel does not have to be present on a PC to produce an Excel compatible file using LabWindows/CVI (or any one of several other C compilers.)
Without having the Excel object loaded on a PC, Here is one way to do what you ask. The caveat, in order to make the file "true Excel", it will have to be opened by Excel, on another PC, and saved in a classic Excel format (i.e. xls or xlsx)...
Here are some easy steps: (see software example below)
Create a text file with a .csv extension to start. Write records to the open file using comma delimited strings and use \n at the end of each. Once file is created, Open it in Excel using *Open as **.* (all files) to allow it to see .csv file types. Once opened, it can saved it in any Excel format you wish.
Code example (this should build with no modifications in LabWindows/CVI)
#include <windows.h>
#include <ansi_c.h>
void main(void)
{
FILE *fp;
fp = fopen ("C:\\tempExtract\\CsvFile.csv", "a");
fputs("every,word,in,this,line,are,fields,in,record,one\n", fp);
fputs("every,word,in,this,line,are,fields,in,record,two\n", fp);
fputs("every,word,in,this,line,are,fields,in,record,three\n", fp);
fclose(fp);
}