I have about 50 scattered cells on my spreadsheet that are
"special". If a user types data into any of these cells, I would
like to immediately check what they typed, modify it how I want,
and then enter the new data into the cell.

For example, suppose a user types "eggs" into cell A1.
I want to change this to "green eggs" immediately after
they type "eggs" in cell A1 and press the Enter key.

I know that this will require me to use the "Worksheet_Change()"
event or subroutine. Is this the only way to handle changes to
the spreadsheet?

I guess I'm just worried about performance. To me it
doesn't make sense to check when ANY cell is changed. It
would be great if I could limit Worksheet_Change() to
only be activated when one of my 50 cells is changed.
Is this possible?