Efficiency of using activeX for Excel

Question

I've been using data logging for our test fixtures in .tsv files, but our engineers want to automate it further by organizing some new data into several sheets, so I'm looking into manipulating Excel directly using ActiveX.
My question is how efficient is it to write this in ActiveX compared to just making a text file? I'm concerned that, since we're going to be writing some 50000 cells or something, that it'll suck up a lot of memory to do it through ActiveX. 
Is this a legitimate concern, or am I just being paranoid?
Anything worth doing is worth over-doing.
LabVIEW Junkie

Answer 1

Thanks for all the help, guys! 
A couple of things -- first off, I'd love to look at that code if you get a chance. But what I'm concerned about is if I create an array of 50000 values or something like that and write it all in one go at the end of the program, two things are going to happen: 1) it's going to take a really long time to finish the program, and 2) if the program crashes in that final step, I'll lose all the data. That second reason is why I currently write a line every cycle to the .tsv file. 
What I'm thinking of doing, is meeting you halfway -- rather than write each cell individually, write each line individually within the spreadsheet. This should reduce the memory used (hopefully) and increase performance.
I haven't really played around with TDMS yet, I'll look into it. A couple questions on that -- does it write in excel format? The reason I ask is the second sheet that I'm supposed to add is not going to contain any changing data -- it's just to store some constants that are set on the front panel. If TDMS stores data in excel format, I can write it to TDMS, transfer to Excel, and then use ActiveX to add the second worksheet with the constants at the end of the program. How's that sound?
Thanks again!
Anything worth doing is worth over-doing.
LabVIEW Junkie