<rant

That's all fine and good.

Here's one thing that I think is important (at least it is to me), I
understand and can explain how the SUMPRODUCT formula works. If I need/want
to change it for other conditions I can do it easily.

Do you really understand these formulas:

=B1-A1+1-INT((B1-MOD(B1-6,7)-A1+7)/7)-INT((B1-MOD(B1-7,7)-A1+7)/7)
=SUM(INT((WEEKDAY(A1-{1,2,3,4,5})+B1-A1)/7))

I don't!

I mean, yeah sure, I know what INT, MOD, SUM and WEEKDAY do. I know what
"plus this minus that divided by this" means. But, can you explain the
*logic of why* the formulas do "plus this minus that divided by this"? I
can't! If I needed/wanted to change those other formulas for other
conditions I don't think It'd be that easy and would take some time to
experiement.

I have the SUM(INT formula in my "library" but I don't suggest it because I
can't explain how it works if someone asks.

I could respond by saying:

You subtract this from that then add this then subtract that and divide by
this but what kind of an explanation is that? That's the explanation of
someone that doesn't understand what they're talking about!

So, my challenge to you is: explain how those formulas work!

</rant
<VBG

--
Biff
Microsoft Excel MVP


"Bernd P" wrote in message
...
Hello,

Now let's have a look how long our formulas take to compute. I ran
them on 5 pairs of dates, 1 day, 1 week, 1 month, 1 year and 10k days
difference and got from FASTEXCEL:
Biff''s SUMPRODUCT 10.61 ms
Mike' NETWORKDAYS 0.23 ms
Biff''s SUM 0.15 ms
Bernd's INT/MOD 0.11 ms

Regards,
Bernd