I need the Today() function to remain static after the cell value is created.

I'm trying to incorporate a column of Today() functions where their values never change once created. Basically, if today's date = X, show Y, if not, zero. And this formula is copied all the way down column A. Once tomorrow becomes the new today, X therefore changes, and now Z will show instead of Y, but I need Y to automatically stay present at the previous row, independent of the actual Today().

A1: =if(today()=B1,Y,0)
A2: =if(today()=B1,Y,0)
A3: =if(today()=B1,Y,0)

... or something along that line. Right now, if B1=today (May 21), A1:A3 = May 21, but I would only like A1 to show May 21. Then, when May 22 hits, A1 remains as Y, but the next row (A2) is now "activated," and A2 now equals Z.

Prefered result:
May 21 May 22 May 23
A1=Y A1=Y A1=Y
A2=0 A2=Z A2=Z
A3=0 A3=0 A3=A

And so forth...

I have no idea how to use a VBA (if needed), so any help would be greatly appreciated.