Adding a small perturbation to duplicate values in two columns

I have two columns of data as follows:

Column A Column B
49 49
49 49
49 49
50 50
51 51
51 51
51 51
51 51
52 52
52 52
52 52
53 53

I would like to write a script that adds +0.0001 to each value that is duplicated in column A. For example, for the three 49 values in column A, it would generate a new column with values as follows 49, 49.001, 49.002. Then for 50, it would not add +.0001 but would ad it to the 51 values (51, 51.001, 51.002, 51.003) and continue this pattern.

For column B, the exact same process should occur, expect -0.0001 is added to each value, therefore the for the three 49 values in column B would generate a new column with values, 49, 48.999, 48.998, 48.997

What would be the best approach to take for this?

Thank you for your help

Thank you, the formula works but i have a data set of over 20,000 cells. I am looking to automate the process with a script.