Conditional Locking of Cells-Excel 2003

I am using Excel 2003. I have built a spreadsheet that is formatted with 12
columns across (one for each month of the year) and then 50-75 rows of data
down that will have activity recorded within each of the twelve month
columns. I have a status row directly below the column headings row that will
indicate whether the month is "open" (meaning open to being updated) or
"closed" (meaning the month is over and no more posting of data is allowed).
What I am trying to do is provide the capability that as the status for a
month is changed to "Closed", all the cells in that month column within each
of the rows would be automatically locked so the data could no longer be
altered. I tried Conditional Formatting, but that seems to only work for
colors, fonts, etc. I'm sure it can be done with a macro of some sorts, but
that seems overly complicated. Has anyone ever faced this problem and come up
with a somewhat simple solution?
I received a suggestion regarding the use of data validation which worked
except for the fact that you can clear the contents of the cell. Does any one
else have any suggestions?
Thanks for your help in advance.
Mike

MikeTVC wrote...
....
What I am trying to do is provide the capability that as the status for a
month is changed to "Closed", all the cells in that month column within
each of the rows would be automatically locked so the data could no longer
be altered. . . .
....
. . . I'm sure it can be done with a macro of some sorts, but
that seems overly complicated. . . .
....

Overly complicated or not, this can ONLY be done by a macro or
manually. If you don't want to do this manually, your only alternative
is using macros.