How to recalculate data using a specific value without changing the initial result?

I have some workbooks with some data as shown below (a sample file also attached for testing and better understanding)

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Now what I want to do is I want to manually give a certain value to CGST/SGST and using that and just changing the values of Rate column (by using upto 4 decimal spaces instead of 2) in the worksheet recalculate the values in the table in such a way that the value of NET AMOUNT remains unchanged.

Can this be done using VBA ?

NOTE:

By using upto 4 decimal spaces

I mean when it is converted to 2 decimal places it would have to be same meaning 812.88 can be 812.8751 but not to 812.8860.

I want to manually give a certain value to CGST/SGST

I mean I cannot simply give any value to it, it would have to be in the range + or - 0.05 of whatever the current CGST/SGST value is in the worksheet.

Could you clarify how the net amount remains unchanged if the CGST is that value divided by 2? For example, if you want the CGST to be doubled, won't the overall net amount also have to double?

EDIT- Ignore question. I misread the requirement