Cumulative Table range rate

Hello,

I have a deduction called "tax" and it works on salary ranges but cumulatively, meaning:

If a salary 2'000$ per month, the tax will be for example:

for the first 1'000$ * 2%  = 20 $

for the next 600$ * 4% = 24  $

and the rest is * 7% = 400 * 7% = 28

so the tax will be: 20 + 24 + 28 = 72$,

I have tried to add a table in the PDBA with these ranges,

0 - 1000: 2%

1000.01 - 1600 : 4%

1600.01 - 99999: 7%

but the system is only looking at the range the salary falls in (which is the last) and multiplying the rate: 2000 * 7% = 140$, which is incorrect for us.

Is there a way to apply our calculations?

Thank you,

Norma