How can i save differnts data in the same file?

[jeanjac]

    Hi all,
i need some help.  I'm working  on a project  for students an th university. We have to devellop  a programm for LEDs measurement so that all the measure data must be save in de same file.  We have develloped the programm, but we have  a big problem to save the measure in the same File.

1. When we do the first  measure , the file must be created and the fisrt data gonna be save in this file that is correct
2. When wie do the second measure, the third  ....  measure, the programm ask us to comfirm the file or where we want save our data
   

We need some help, to know how we can change  or devellop this programm so that, for the first measure , the file must be created and the fisrt data gonna be save in this file,  the second measure the same file must be chose and from the third and more the measure data must be automatically save in this file without the programm ask to chose or to confirme a file? 
I attach a part off this programmm
Thanks

[J3000]

Move the "File Dialog" where you open your new file out of the while loop. Only pass the refnum inside the loop.

[J3000]

Forgot to mention, use "write to spreadsheet.vi" inside the loop, and choose "append to file"