If you had a macro program or keyboard recorder, you could record this
sequence of keystrokes and assign it to a shortcut of your choice.
If he wants to operate on just the part of the formula that he has selected,
you can't record or run a macro to do it.
When you are editing in the formula bar, you can't turn on the macro recorder.
When you are editing in the formula bar, you can't run a macro, either.
If he always wanted to put parens around, say, the 5th through the 10th
characters, that could be automated with a macro. But he is out of luck if the
position and length is variable.