Finding the Min Positive Value of Dynamic Data

I searched the forum but couldn't find what I was looking for. I've found lots of solutions for finding the min positive value of an array, but let me elaborate on my problem.

One cell in my sheet is returning values from a DDE link from a third-party trading platform. The cell continuously updates Net Profit/Loss. I want two different cells to record the max value and min value that had appeared throughout the day. Assume Net P/L cell was A1, and the Max cell was B1, Min cell was B2.

So I've tried the obvious attempt in B1, =max(a1,b1) which will only work if my Net P/L is positive. But if my P/L is negative it will remain zero, since that was the default value of B1 before calculations begin. Likewise, my min in B2 will remain zero, unless my Net P/L is negative. So on days where I am only making positive cumulative profits on my trading positions, I have no record of what my lowest level of profit was throughout the day.

I have tried other circular references such as seeking the max value in cell b1: =if(b1>a1, b1, a1) but this of course returns the same problematic result.

I've googled this, and probably should have just asked for help sooner.

Thanks.

That solves the problem as I described it. I now have a whole host of other problems, but I think they belong in new thread. /me ups your rep