try this
<b>Excel 2007</b><table cellpadding="2.5px" rules="all" style=";background-color: #FFFFFF;border: 1px solid;border-collapse: collapse; border-color: #A6AAB6"><colgroup><col width="25px" style="background-color: #E0E0F0" /><col /><col /><col /><col /></colgroup><thead><tr style=" background-color: #E0E0F0;text-align: center;color: #161120"><th></th><th>B</th><th>C</th><th>D</th><th>E</th></tr></thead><tbody><tr ><td style="color: #161120;text-align: center;">1</td><td style="text-align: right;;">01/07/2011</td><td style="text-align: right;;"></td><td style="text-align: right;;"></td><td style="text-align: right;;">100</td></tr><tr ><td style="color: #161120;text-align: center;">2</td><td style="text-align: right;;">15/07/2011</td><td style="text-align: right;;"></td><td style="text-align: right;;"></td><td style="text-align: right;;">100</td></tr><tr ><td style="color: #161120;text-align: center;">3</td><td style="text-align: right;;">25/07/2011</td><td style="text-align: right;;"></td><td style="text-align: right;;"></td><td style="text-align: right;;">100</td></tr><tr ><td style="color: #161120;text-align: center;">4</td><td style="text-align: right;;">01/08/2011</td><td style="text-align: right;;"></td><td style="text-align: right;;"></td><td style="text-align: right;;">100</td></tr><tr ><td style="color: #161120;text-align: center;">5</td><td style="text-align: right;;">14/08/2011</td><td style="text-align: right;;"></td><td style="text-align: right;;"></td><td style="text-align: right;;">100</td></tr><tr ><td style="color: #161120;text-align: center;">6</td><td style="text-align: right;;">14/08/2011</td><td style="text-align: right;;"></td><td style="text-align: right;;"></td><td style="text-align: right;;">100</td></tr><tr ><td style="color: #161120;text-align: center;">7</td><td style="text-align: right;;"></td><td style="text-align: right;;"></td><td style="text-align: right;;"></td><td style="text-align: right;;"></td></tr><tr ><td style="color: #161120;text-align: center;">8</td><td style=";">18
Total Invoice amounts Before 25/07/2011</td><td style="text-align: right;;"></td><td style="text-align: right;;">300</td><td style="text-align: right;;"></td></tr></tbody></table><p style="width:3.6em;font-weight:bold;margin:0;padding:0.2em 0.6em 0.2em 0.5em;border: 1px solid #A6AAB6;border-top:none;text-align: center;background-color: #E0E0F0;color: #161120">Sheet1</p><br /><br /><table width="85%" cellpadding="2.5px" rules="all" style=";border: 2px solid black;border-collapse:collapse;padding: 0.4em;background-color: #FFFFFF" ><tr><td style="padding:6px" ><b>Array Formulas</b><table cellpadding="2.5px" width="100%" rules="all" style="border: 1px solid;text-align:center;background-color: #FFFFFF;border-collapse: collapse; border-color: #A6AAB6"><thead><tr style=" background-color: #E0E0F0;color: #161120"><th width="10px">Cell</th><th style="text-align:left;padding-left:5px;">Formula</th></tr></thead><tbody><tr><th width="10px" style=" background-color: #E0E0F0;color: #161120">D8</th><td style="text-align:left">{=SUM(<font color="Blue">IF(<font color="Red">DATEVALUE(<font color="Green">RIGHT(<font color="Purple">B8,11</font>)</font>)>=B1:B6,E1:E6</font>)</font>)}</td></tr></tbody></table><b>Entered with Ctrl+Shift+Enter.</b> If entered correctly, Excel will surround with curly braces {}.
<b>Note: Do not try and enter the {} manually yourself</b></td></tr></table><br />