Example data
If you copy and paste as values then sort by column "C" the "" cells have a high value
<b>Excel 2010</b><table cellpadding="2.5px" rules="all" style=";background-color: #FFFFFF;border: 1px solid;border-collapse: collapse; border-color: #BBB"><colgroup><col width="25px" style="background-color: #DAE7F5" /><col /><col /><col /></colgroup><thead><tr style=" background-color: #DAE7F5;text-align: center;color: #161120"><th></th><th>A</th><th>B</th><th>C</th></tr></thead><tbody><tr ><td style="color: #161120;text-align: center;">1</td><td style=";">A/C</td><td style=";">Amount</td><td style=";">Total</td></tr><tr ><td style="color: #161120;text-align: center;">2</td><td style=";">abc</td><td style="text-align: right;;">10</td><td style="text-align: right;;">60</td></tr><tr ><td style="color: #161120;text-align: center;">3</td><td style=";">abc</td><td style="text-align: right;;">20</td><td style=";"></td></tr><tr ><td style="color: #161120;text-align: center;">4</td><td style=";">abc</td><td style="text-align: right;;">30</td><td style=";"></td></tr><tr ><td style="color: #161120;text-align: center;">5</td><td style=";">def</td><td style="text-align: right;;">10</td><td style="text-align: right;;">60</td></tr><tr ><td style="color: #161120;text-align: center;">6</td><td style=";">def</td><td style="text-align: right;;">20</td><td style=";"></td></tr><tr ><td style="color: #161120;text-align: center;">7</td><td style=";">def</td><td style="text-align: right;;">30</td><td style=";"></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 #BBB;border-top:none;text-align: center;background-color: #DAE7F5;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>Worksheet 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: #BBB"><thead><tr style=" background-color: #DAE7F5;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: #DAE7F5;color: #161120">C2</th><td style="text-align:left">=IF(<font color="Blue">A2=A1,"",SUMIF(<font color="Red">A:A,A2,B:B</font>)</font>)</td></tr><tr><th width="10px" style=" background-color: #DAE7F5;color: #161120">C3</th><td style="text-align:left">=IF(<font color="Blue">A3=A2,"",SUMIF(<font color="Red">A:A,A3,B:B</font>)</font>)</td></tr><tr><th width="10px" style=" background-color: #DAE7F5;color: #161120">C4</th><td style="text-align:left">=IF(<font color="Blue">A4=A3,"",SUMIF(<font color="Red">A:A,A4,B:B</font>)</font>)</td></tr><tr><th width="10px" style=" background-color: #DAE7F5;color: #161120">C5</th><td style="text-align:left">=IF(<font color="Blue">A5=A4,"",SUMIF(<font color="Red">A:A,A5,B:B</font>)</font>)</td></tr><tr><th width="10px" style=" background-color: #DAE7F5;color: #161120">C6</th><td style="text-align:left">=IF(<font color="Blue">A6=A5,"",SUMIF(<font color="Red">A:A,A6,B:B</font>)</font>)</td></tr><tr><th width="10px" style=" background-color: #DAE7F5;color: #161120">C7</th><td style="text-align:left">=IF(<font color="Blue">A7=A6,"",SUMIF(<font color="Red">A:A,A7,B:B</font>)</font>)</td></tr></tbody></table></td></tr></table><br />