Add a formula after cell text content

[King Mustard]

I have a Wages worksheet.

I have a Pay amount (manually entered, Currency format, no decimal places) and a Tax amount (manually entered, Currency format, two decimal places).

An an example, the Pay cell contains "£1000" and the Tax cell contains "£100".

Is it possible to make the Tax cell show "£100 (10%)"? (with the 10% being calculated)

 

[mikerickson]

How does the tax cell get the 100, is it the result of a formula or does the user enter the value?

 

[King Mustard]

How does the tax cell get the 100, is it the result of a formula or does the user enter the value?

Sorry, it's manually entered.

 

[mikerickson]

That's not good.
When a user enters a value into a cell, the previous contents (including any formula that would create a percentage) are gone.
This would require VBA. A helper column with a formula would be easier