I think you had it right the first time. (See the line in red.) If so, you can try this formula:
| A | B | C | D | E |
---|
Amount | Bonus | Tier | Rate | Differential Rate | |
| | | | | |
| | | | | |
| | | | | |
| | | | | |
| | | | | |
<tbody>
[TD="align: center"]1[/TD]
[TD="align: center"]2[/TD]
[TD="align: right"]65000[/TD]
[TD="align: right"]1275[/TD]
[TD="align: right"]0[/TD]
[TD="align: right"]0%[/TD]
[TD="align: right"]0%[/TD]
[TD="align: center"]3[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"]35000[/TD]
[TD="align: right"]3.50%[/TD]
[TD="align: right"]3.50%[/TD]
[TD="align: center"]4[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"]50000[/TD]
[TD="align: right"]5.00%[/TD]
[TD="align: right"]1.50%[/TD]
[TD="align: center"]5[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"]75000[/TD]
[TD="align: right"]10%[/TD]
[TD="align: right"]5%[/TD]
[TD="align: center"]6[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"]100000[/TD]
[TD="align: right"]15%[/TD]
[TD="align: right"]5%[/TD]
</tbody>
Sheet7
[TABLE="width: 85%"]
<tbody>[TR]
[TD]
Worksheet Formulas[TABLE="width: 100%"]
<tbody>[TR="bgcolor: #DAE7F5"]
[TH]Cell[/TH]
[TH="align: left"]Formula[/TH]
[/TR]
[TR]
[TH="bgcolor: #DAE7F5"]B2[/TH]
[TD="align: left"]=SUMPRODUCT(
--(A2>$C$2:$C$6),(A2-$C$2:$C$6),$E$2:$E$6)[/TD]
[/TR]
[TR]
[TH="bgcolor: #DAE7F5"]E2[/TH]
[TD="align: left"]=D2[/TD]
[/TR]
[TR]
[TH="bgcolor: #DAE7F5"]E3[/TH]
[TD="align: left"]=D3-D2[/TD]
[/TR]
</tbody>[/TABLE]
[/TD]
[/TR]
</tbody>[/TABLE]
Build a table like C1:E6. Put your rates in D, and put the formulas in E to create the differentials. Then the formula in B2 will give you your bonus.
Hope this helps!