Excel pattern recognition

Hi,  I am trying to calculate some percentages and the steps for achieving the same is as follows

Steps

1. choose the  cell or sum of the cells below
2. Subtract this with next corresponding cell value
3. Divide it by the aforementioned sum
4. Multiply the result with 100

Example

=((A1)-(B1))/(A1)*100

=((A1+A2)-(B2))/(A1+A2)*100

=((A1+A2+A3)-(B3))/(A1+A2+A3)*100

.

.

.

Pattern is not being recognized. Instead of incrementing the cells for the next step, it's copying the formulas and calculating the values.

Thank you in advance.