Fwiw, the response below was posted to your multi-post in .links ..
(you should not multi-post)
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One approach to achieve it is illustrated in this sample construct:
http://www.savefile.com/files/638369
Apportioning days within a date range under correct month cols.xls

Startdates in E3 down, Enddates in F3 down
1st of month dates (formatted as "mmm-yy") listed in L2 across, viz: Jan-07,
Feb-07, etc

Then in L3:
=IF(TEXT(L$2,"mmm-yy")=TEXT($E3,"mmm-yy"),DATE(YEAR(L$2),MONTH(L$2)+1,0)-$E3+1,IF(TEXT(L$2,"mmm-yy")=TEXT($F3,"mmm-yy"),$F3-DATE(YEAR(L$2),MONTH(L$2),1)+1,IF(AND(DATE(YEAR(L$ 2),MONTH(L$2),1)DATE(YEAR($E3),MONTH($E3),1),DATE (YEAR(L$2),MONTH(L$2),1)<DATE(YEAR($F3),MONTH($F3) ,1)),DAY(DATE(YEAR(L$2),MONTH(L$2)+1,0)),"")))

Copy L3 across/fill down as far as required. This will return the number of
days under each month's col as appropriate (between the startdates and
enddates in cols E and F)
--
Max
Singapore
http://savefile.com/projects/236895
xdemechanik
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