You want to do it on a cumulative basis, so assuming I am correct, you want this:
<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 style="background-color: #DAE7F5" /><col /><col /><col /><col /><col /><col /><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><th>D</th><th>E</th><th>F</th><th>G</th><th>H</th><th>I</th></tr></thead><tbody><tr ><td width="25px" style="color: #161120;text-align: center;">1</td><td width="63px" style="font-weight: bold;;">Name</td><td width="63px" style="font-weight: bold;;">Bookings</td><td width="63px" style="font-weight: bold;;">Commission</td><td width="63px" style="font-weight: bold;text-align: right;;"></td><td width="63px" style="font-weight: bold;text-align: right;;"></td><td width="63px" style="font-weight: bold;;">Commission</td><td width="63px" style="font-weight: bold;text-align: right;;"></td><td width="63px" style="font-weight: bold;text-align: right;;"></td><td width="63px" style="font-weight: bold;text-align: right;;"></td></tr><tr ><td width="25px" style="color: #161120;text-align: center;">2</td><td width="63px" style=";">Integis</td><td width="63px" style="text-align: right;;">$10,500</td><td width="63px" style="text-align: right;;">1050</td><td width="63px" style="text-align: right;;"></td><td width="63px" style="text-align: right;;"></td><td width="63px" style="font-weight: bold;;">Lower limit</td><td width="63px" style="font-weight: bold;;">Upper limit</td><td width="63px" style="font-weight: bold;;">Rate</td><td width="63px" style="font-weight: bold;;">Differential Rate</td></tr><tr ><td width="25px" style="color: #161120;text-align: center;">3</td><td width="63px" style=";">ABC</td><td width="63px" style="text-align: right;;">$17,500</td><td width="63px" style="text-align: right;;">3450</td><td width="63px" style="text-align: right;;"></td><td width="63px" style="text-align: right;;"></td><td width="63px" style="text-align: right;;">$0</td><td width="63px" style="text-align: right;;">$15,000</td><td width="63px" style="text-align: right;;">10%</td><td width="63px" style="text-align: right;;">10%</td></tr><tr ><td width="25px" style="color: #161120;text-align: center;">4</td><td width="63px" style=";">Today Company</td><td width="63px" style="text-align: right;;">$30,000</td><td width="63px" style="text-align: right;;">9700</td><td width="63px" style="text-align: right;;"></td><td width="63px" style="text-align: right;;"></td><td width="63px" style="text-align: right;;">$15,000</td><td width="63px" style="text-align: right;;">$36,000</td><td width="63px" style="text-align: right;;">15%</td><td width="63px" style="text-align: right;;">5%</td></tr><tr ><td width="25px" style="color: #161120;text-align: center;">5</td><td width="63px" style=";">ACME</td><td width="63px" style="text-align: right;;">$58,000</td><td width="63px" style="text-align: right;;">24200</td><td width="63px" style="text-align: right;;"></td><td width="63px" style="text-align: right;;"></td><td width="63px" style="text-align: right;;">$36,000</td><td width="63px" style="text-align: right;;">$45,000</td><td width="63px" style="text-align: right;;">20%</td><td width="63px" style="text-align: right;;">5%</td></tr><tr ><td width="25px" style="color: #161120;text-align: center;">6</td><td width="63px" style="text-align: right;;"></td><td width="63px" style="text-align: right;;"></td><td width="63px" style="text-align: right;;"></td><td width="63px" style="text-align: right;;"></td><td width="63px" style="text-align: right;;"></td><td width="63px" style="text-align: right;;">$45,000</td><td width="63px" style="text-align: right;;">$56,250</td><td width="63px" style="text-align: right;;">25%</td><td width="63px" style="text-align: right;;">5%</td></tr><tr ><td width="25px" style="color: #161120;text-align: center;">7</td><td width="63px" style="text-align: right;;"></td><td width="63px" style="text-align: right;;"></td><td width="63px" style="text-align: right;;"></td><td width="63px" style="text-align: right;;"></td><td width="63px" style="text-align: right;;"></td><td width="63px" style="text-align: right;;">$56,250</td><td width="63px" style="text-align: right;;"></td><td width="63px" style="text-align: right;;">25%</td><td width="63px" style="text-align: right;;">0%</td></tr></tbody></table><p style="width:3.6em;font-weight:bold;margin:0;padding:0.2em 0.6em 0.2em 0.5em;border: 1px solid #BBB;border-top:none;text-align: center;background-color: #DAE7F5;color: #161120">Sheet1</p><br /><br /><table cellpadding="2.5px" rules="all" style=";border: 2px solid black;border-collapse:collapse;padding: 0.4em;background-color: #FFFFFF" ><tr><td style="padding:6px" ><b>Worksheet Formulas</b><table cellpadding="2.5px" width="100%" rules="all" style="border: 1px solid;text-align:center;background-color: #FFFFFF;border-collapse: collapse; border-color: #BBB"><thead><tr style=" background-color: #DAE7F5;color: #161120"><th width="10px">Cell</th><th style="text-align:left;padding-left:5px;">Formula</th></tr></thead><tbody><tr><th width="10px" style=" background-color: #DAE7F5;color: #161120">C2</th><td style="text-align:left">=SUMPRODUCT(<font color="Blue">(<font color="Red">SUM(<font color="Green">$B$2:$B2</font>)>$F$3:$F$7</font>)+0,(<font color="Red">SUM(<font color="Green">$B$2:$B2</font>)-$F$3:$F$7</font>)+0,$I$3:$I$7</font>)</td></tr><tr><th width="10px" style=" background-color: #DAE7F5;color: #161120">I3</th><td style="text-align:left">=H3-N(<font color="Blue">H2</font>)</td></tr></tbody></table></td></tr></table><br />
Formula in C2 is copied down for the number of records you hve, and formula in I3 is also copied down. I made an assumption that 25% was the highest rate of commission you pay, hence the entry in H7 of the table.