It's going to be one or the other: either you know the start/end date and use that to spread your values, or you know where the spreads fall and determine the start/end date from there. But along these lines:
<table border="1" cellspacing="0" cellpadding="0" style="font-family:Calibri,Arial; font-size:11pt; background-color:#ffffff; padding-left:2pt; padding-right:2pt; "> <colgroup><col style="font-weight:bold; width:30px; " /><col style="width:64px;" /><col style="width:64px;" /><col style="width:64px;" /><col style="width:64px;" /><col style="width:64px;" /><col style="width:64px;" /><col style="width:64px;" /><col style="width:64px;" /><col style="width:64px;" /><col style="width:64px;" /><col style="width:64px;" /><col style="width:64px;" /><col style="width:64px;" /><col style="width:64px;" /><col style="width:64px;" /></colgroup><tr style="background-color:#cacaca; text-align:center; font-weight:bold; font-size:8pt; "><td >*</td><td >A</td><td >B</td><td >C</td><td >D</td><td >E</td><td >F</td><td >G</td><td >H</td><td >I</td><td >J</td><td >K</td><td >L</td><td >M</td><td >N</td><td >O</td></tr><tr style="height:18px ;" ><td style="font-size:8pt; background-color:#cacaca; text-align:center; " >1</td><td >*</td><td >*</td><td style="text-align:right; ">Jan-11</td><td style="text-align:right; ">Feb-11</td><td style="text-align:right; ">Mar-11</td><td style="text-align:right; ">Apr-11</td><td style="text-align:right; ">May-11</td><td style="text-align:right; ">Jun-11</td><td style="text-align:right; ">Jul-11</td><td style="text-align:right; ">Aug-11</td><td style="text-align:right; ">Sep-11</td><td style="text-align:right; ">Oct-11</td><td style="text-align:right; ">Nov-11</td><td style="text-align:right; ">Dec-11</td><td style="text-align:right; ">Jan-12</td></tr><tr style="height:18px ;" ><td style="font-size:8pt; background-color:#cacaca; text-align:center; " >2</td><td style="text-align:right; ">Jul-11</td><td style="text-align:right; ">Oct-11</td><td >*</td><td >*</td><td >*</td><td >*</td><td >*</td><td >*</td><td >*</td><td >*</td><td >*</td><td >*</td><td >*</td><td >*</td><td >*</td></tr><tr style="height:18px ;" ><td style="font-size:8pt; background-color:#cacaca; text-align:center; " >3</td><td >*</td><td >*</td><td style="text-align:right; ">0</td><td style="text-align:right; ">0</td><td style="text-align:right; ">0</td><td style="text-align:right; ">0</td><td style="text-align:right; ">0</td><td style="text-align:right; ">0</td><td style="text-align:right; ">25</td><td style="text-align:right; ">25</td><td style="text-align:right; ">25</td><td style="text-align:right; ">25</td><td style="text-align:right; ">0</td><td style="text-align:right; ">0</td><td style="text-align:right; ">0</td></tr></table><br /><table style="font-family:Arial; font-size:10pt; border-style: groove ;border-color:#00ff00;background-color:#fffcf9; color:#000000; "><tr><td ><b>Spreadsheet Formulas</b></td></tr><tr><td ><table border = "1" cellspacing="0" cellpadding="2" style="font-family:Arial; font-size:9pt;"><tr style="background-color:#cacaca; font-size:10pt;"><td >Cell</td><td >Formula</td></tr><tr><td >A2</td><td >{=INDEX(C1:O1, MATCH<span style=' color:008000; '>(FALSE, C3:O3=0, 0)</span>)}</td></tr><tr><td >B2</td><td >{=INDEX($C$1:$O$1, MAX<span style=' color:008000; '>(ROW<span style=' color:#0000ff; '>(INDIRECT<span style=' color:#ff0000; '>("1:"&COUNTA<span style=' color:#804000; '>(C3:O3)</span>)</span>)</span>*TRANSPOSE<span style=' color:#0000ff; '>(C3:O3>0)</span>)</span>)}</td></tr></table></td></tr><tr><td ><span style=' font-family:Arial,Arial; font-size:9pt; font-weight:bold;'>Formula Array:</span><span style=' font-family:Arial,Arial; font-size:9pt;'><br />Produce enclosing </span><span style=' font-family:Arial,Arial; font-size:9pt; font-weight:bold;'>{ }</span><span style=' font-family:Arial,Arial; font-size:9pt;'> by entering<br />formula with CTRL+SHIFT+ENTER!</span></td></tr></table>