DDE in loop

[LV_newbie]

Hi.
I have a program with 9 LEDs in a For Loop. After each LED is tested,
it sends the data to Excel through DDE. It is working fine for the
first time through the whole For Loop, but when it goes through the
loop again (0-8 afor the second time), my original data in Excel gets
replaced by this new data. It is because I specify what columns to
insert the data into. Is there any way of updating my string input (on
where to place the data) so that it changes with each for loop?