I have a rather complicated question (at least I think it is...)

I have a cell that shows a number. That number is not constant, but
changing every couple of seconds. Let's say it shows the profit and
loss (p/l) level in USD derived from an open position in some a stock.

Once p/l reaches $25,000 and/or goes above, I want excel to give me a
warning (a pop-up window plus an audio one if possible) when the p/l
level reaches 67% of the maximum level it had been.

So, for example, if the p/l has surpassed $25,000 and reached $100,000
and than dropped to $50,000 but never returned to $100,000, excel will
give me the warning when it reaches $67,000 (67% of $100,000).

In the case $25,000 was the highest level and the p/l dropped
thereafter, excel will keep the "67%" rule and warn me at $16,750 (67%
of 25,000).

Can this be done at all?

Thanks,

Amir