You could do:
=MAX(0,MIN(C2,DATE(2009,3,0))-MAX(D2,DATE(2009,2,0)))
where you will need to alter the 2009 value to the February year of interest. There's probably a much slicker way of doing this...
Richard, Was giving me this result, didnt seem to work on quite a few of them.
<TABLE style="WIDTH: 159pt; BORDER-COLLAPSE: collapse" cellSpacing=0 cellPadding=0 width=213 border=0 x:str><COLGROUP><COL style="WIDTH: 53pt; mso-width-source: userset; mso-width-alt: 2596" span=2 width=71><COL style="WIDTH: 53pt; mso-width-source: userset; mso-width-alt: 2596" width=71><TBODY><TR style="HEIGHT: 12.75pt" height=17><TD class=xl24 style="BORDER-RIGHT: #d4d0c8; BORDER-TOP: #d4d0c8; BORDER-LEFT: #d4d0c8; WIDTH: 53pt; BORDER-BOTTOM: #d4d0c8; HEIGHT: 12.75pt; BACKGROUND-COLOR: transparent" align=right width=71 height=17 x:num="39871">
27/02/2009</TD><TD class=xl24 style="BORDER-RIGHT: #d4d0c8; BORDER-TOP: #d4d0c8; BORDER-LEFT: #d4d0c8; WIDTH: 53pt; BORDER-BOTTOM: #d4d0c8; BACKGROUND-COLOR: transparent" align=right width=71 x:num="39872">
28/02/2009</TD><TD class=xl25 style="BORDER-RIGHT: #d4d0c8; BORDER-TOP: #d4d0c8; BORDER-LEFT: #d4d0c8; WIDTH: 53pt; BORDER-BOTTOM: #d4d0c8; BACKGROUND-COLOR: transparent" align=right width=71 x:num x:fmla="=MAX(0,MIN(A1,DATE(2009,3,0))-MAX(B1,DATE(2009,2,0)))">
0</TD></TR></TBODY></TABLE>
<TABLE style="WIDTH: 159pt; BORDER-COLLAPSE: collapse" cellSpacing=0 cellPadding=0 width=213 border=0 x:str><COLGROUP><COL style="WIDTH: 53pt; mso-width-source: userset; mso-width-alt: 2596" span=2 width=71><COL style="WIDTH: 53pt; mso-width-source: userset; mso-width-alt: 2596" width=71><TBODY><TR style="HEIGHT: 12.75pt" height=17><TD class=xl24 style="BORDER-RIGHT: #d4d0c8; BORDER-TOP: #d4d0c8; BORDER-LEFT: #d4d0c8; WIDTH: 53pt; BORDER-BOTTOM: #d4d0c8; HEIGHT: 12.75pt; BACKGROUND-COLOR: transparent" align=right width=71 height=17 x:num="39868">
24/02/2009</TD><TD class=xl24 style="BORDER-RIGHT: #d4d0c8; BORDER-TOP: #d4d0c8; BORDER-LEFT: #d4d0c8; WIDTH: 53pt; BORDER-BOTTOM: #d4d0c8; BACKGROUND-COLOR: transparent" align=right width=71 x:num="39869">
25/02/2009</TD><TD class=xl25 style="BORDER-RIGHT: #d4d0c8; BORDER-TOP: #d4d0c8; BORDER-LEFT: #d4d0c8; WIDTH: 53pt; BORDER-BOTTOM: #d4d0c8; BACKGROUND-COLOR: transparent" align=right width=71 x:num x:fmla="=MAX(0,MIN(A1,DATE(2009,3,0))-MAX(B1,DATE(2009,2,0)))">
0</TD></TR></TBODY></TABLE>
<TABLE style="WIDTH: 159pt; BORDER-COLLAPSE: collapse" cellSpacing=0 cellPadding=0 width=213 border=0 x:str><COLGROUP><COL style="WIDTH: 53pt; mso-width-source: userset; mso-width-alt: 2596" span=2 width=71><COL style="WIDTH: 53pt; mso-width-source: userset; mso-width-alt: 2596" width=71><TBODY><TR style="HEIGHT: 12.75pt" height=17><TD class=xl24 style="BORDER-RIGHT: #d4d0c8; BORDER-TOP: #d4d0c8; BORDER-LEFT: #d4d0c8; WIDTH: 53pt; BORDER-BOTTOM: #d4d0c8; HEIGHT: 12.75pt; BACKGROUND-COLOR: transparent" align=right width=71 height=17 x:num="39860">
16/02/2009</TD><TD class=xl24 style="BORDER-RIGHT: #d4d0c8; BORDER-TOP: #d4d0c8; BORDER-LEFT: #d4d0c8; WIDTH: 53pt; BORDER-BOTTOM: #d4d0c8; BACKGROUND-COLOR: transparent" align=right width=71 x:num="39933">
30/04/2009</TD><TD class=xl25 style="BORDER-RIGHT: #d4d0c8; BORDER-TOP: #d4d0c8; BORDER-LEFT: #d4d0c8; WIDTH: 53pt; BORDER-BOTTOM: #d4d0c8; BACKGROUND-COLOR: transparent" align=right width=71 x:num x:fmla="=MAX(0,MIN(A1,DATE(2009,3,0))-MAX(B1,DATE(2009,2,0)))">
0</TD></TR></TBODY></TABLE>