Offset and Look value upside from ever changing last corresponding row

Sample Workbook with data in version 97-2003 is attached for ready reference.

I have worksheet where I keep data from Row 30 onwards and it keeps expanding.

In order to see what is the last uniques record from Column B having DATE (dd-mmm-yy), I use following formula in Cell C10 to get the last date:

=LOOKUP(2,1/(B:B<>""),B:B)

In Cell D10, I use following formula to get corresponding Row number to find what that last cell is:

=MATCH(C10,B:B,0)

Now, I want to retrieve certain values from Column L (data begins from row 30 onward, and will keep expanding along with new dates getting added in Column B).

Since last date / transaction would appear at bottom, I want to scroll up, say 50 (control number, I have stores, to keep flexibility) in Cell F9, and G9.

Now, I am confused, how to use OFFSET function (Or other combination, such that Cell F10 should show Max value, and G10 Min Value from Column L, with following rational.

From Last date appearing in Cell B258 , formula should look through Column L UPWARD side to locate, Max / Min value from Control figure given in Cell F9 & G9.

Currently, I have shown manually in Cell M257, N257 , Max and Min value starting from Row 258 and ignoring that cell, moving range up -50 row upside, Max and Min value.

Last date / data / row will keep increasing day by day, and Control figure (currently 50) may also change to see the other relevant similar details.

Thanks