Replacing Formula with Data

[unixguru]

Been a few years - maybe 10 or 12 - since I've set up spreadsheets.
I remember being able to use a pointer created by counting the number of rows that have data and then adding 1 so I will start in the next blank row.
I am having problems adding the column to the index ---
ie - I calculate the next row is 12 and I [always start in column B...
What I want to do is goto cell B12 and start entering data.

A second thing I used to do was check a cell ( B12) for data - actually for 'not blank' - and then enter today's date in A12...

=IF(B12="";"";Today()) <<== This accomplishes that easily.
Problem is When I open the spreadsheet tomorrow the date will be changed to tomorrow's date because cell B12 will have data in it.

What I used to do was overwrite the formula that puts the date into cell A12.
Another way I did it was to calculate the date in a separate cell like i do the row index, reference the correct 'B' row checking for data - or 'not blank' ....Then copy the date to the correct A cell....

Hope I didn't confuse you too much with the explanation of what I need.

Thanks for any help.....
Larry