Sheet2!A1:A133 is the 1st-of-the-months -- I did A1:A2 manually, then dragged the pair of them down.
B1:B132 are basic formulas.
Press CTRL+F3 to show the Names dialog box. Click on "Firsts" in the list of names, to show that the
named range Sheet2!$A$1:$A$133 refers to those cells (so if you update that list, you'll need to update the "Refers to" too -- don't forget that).
Select Sheet1!K1, check Data > Validation to see that the named range "Firsts" is the validation source for that cell. Cancel the dialog.
The Sheet1!L1 formula gives you the row in column A where K1 value is. The Sheet1!M1 formula combines INDEX and MATCH to give number of days in the month according to K1.
Press CTRL+F3 again. The second named range is
mmm. Its "Refers to" is:
=OFFSET(Sheet1!$A$1,Sheet1!$L$1-1,0,Sheet1!$M$1,1)
That's a
dynamic named range, with 4 "parameters".
OFFSET(Sheet1!$A$1,Sheet1!$L$1-1,0 means the range
starts at [Sheet1!$L$1-1] cells down and 0 cells to the right of A1. So when K1 = 1-Jan-99, then L1 = 2, thus the range starts at A1 offset by (2-1) cells down and 0 cells to the right -- i.e., A2.
Then you have
Sheet1!$M$1,1 dictating how many rows down
and across from the start cell the range extends. So for K1 = 1-Jan-99, M1 = 31, making the range from A2 down 31 rows total & 1 column across. Or A2:A32.
K1 = 1-Feb-99, L1 = 33, range starts at A33, M1 = 28, range extends over 28 rows & 1 column. And so on.
Don't worry if this is really confusing. It took me literally years to "get" dynamic named ranges. A
true Excel genius could explain it way better than me.
ETA: about 60 miles north of London, England. Michigan's a state, right?
