Calculation

I need to apply the % factor in calculation.

I need multiply step 1 (X) with step 2 and arrive at step 3.

Step1 = Amount is stored in 'Account1' and datasource 'DS1'.

Step2 = % increment is stored in 'Account1' and datasource 'DS2'.

Step 3= New amount to be stroed in 'Account1' and data source 'DS3'.

I need to write logic as follows: Step1 * Step2(%+100) = Step3

How would the syntex could be drafted in this scenario.

Appreciate input.