By way of background for those spared the pain of Excel, the alphanumeric designations for cells in the top row of an Excel spreadsheet are:   A1..Z1   followed by AA1..AZ1   followed by BA1..BZ1   and so on...

However, the standard (or so I'm led to believe) routine for identifying the last-populated-column,

$Win32::OLE::Warn = 3;                     # die ( UGLY ) on errors...
my $Excel =  Win32::OLE->new('Excel.Application', 'Quit');
my $Book = $Excel->Workbooks->Open($FN);
my $Sheet = $Book->Worksheets(1);         # select worksheet number 1

$LastCol = $Sheet->UsedRange->Find({What=>"*",
        SearchDirection=>xlPrevious,
        SearchOrder=>xlByColumns})->{Column};
[download]

... returns a decimal number (equal to the number of columns) in $LastCol).

That's a PITA, because Win32::OLE accepts ONLY an alphanumeric, as in this next snippet, to obtain the date itself from Row1, Last_Column,:

$lastdate =  $Sheet->Range("CK1")->Win32::OLE::valof({'Value'});
print "Data is THROUGH $lastdate \n\n";
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$lastdate =  $Sheet->Range($LastCol)->Win32::OLE::valof({'Value'});
print "Data is THROUGH $lastdate \n\n";
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Win32::OLE(0.1702) error 0x800a03ec<br>
    in METHOD/PROPERTYGET "Range" at getdrills_time3.pl line 32
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Hence, what I wish to do is convert the numeric value of $LastCol ( "89" is what Win32:0LE returns for the last_column of a spreadsheet with data in "CK" columns) to its equivalent alphanumeric designator, CK1, which could then be passed to the last previous code snippet in place of $LastCol.

Update: 2 hours; 3 valuable answers to a l-o-o-n-g SOPW. Monastery ++
Now to try each, with thanks to John, bmann and traveler!

Further update (200511231145): Again, ++ each of you. For future SOPW,

• There seem to be a "gotcha'" I had not specified nor considered: behavior (under w2k, anyway) seems to be dependent on whether or not the data_file is open in Excel (and may vary from OS to OS) and perhaps also on some peculiarity of my full (ungolfed) code).
• Working on w2k with Excel NOT open, I found that the suggestions below DO, in fact, WORK, but that [recusive ref to preceding, ?special case?] I MUST invoke Win32:OLE's "valof" to get the actual date, rather than a memory reference to that date, as in the following example:

$lastdate = $Sheet->Cells(1, $LastCol)->Win32::OLE::valof ({ 'Value'})
+;
print "jcmcnamara's version: $lastdate \n";
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The same applies to bmann's first alternative while his second suggestion appears to depend on having the data_file OPEN in Excel.

And FWIW, for the script I'm actually passing on to my Fire Department, I opted to incorporate traveler's version (again, modified with addition of the valof function) solely because it may be slightly clearer, even if more intimidating, to some future maintainer... which concern is given high priority because I see NO immediate prospect that we'll have another perl_person in the house, but would like the code clear enough to perhaps encourage someone. IOW, if a roof comes in on \me, I'm trying to make it easier for the Dept to find someone to deal with next year's changes... and those which follow.

CAUTION: re all the points in this update, YMMV!