Put your words (without brackets or quotes) in column H, starting in cell H1
Put "" in cell G1
Put  in cell G2
Cell B1 contains Yes or No
In cell A1 put this formula:=IF($B$1="Yes",LEFT($G$1,1)&H1&RIGHT($G$1,1),LEFT($G$2,1)&H1&RIGHT($G$2,1))
Note the $ signs in some parts of the formula
Extend the formula in A1 by dragging it down as many rows as you have words in column H.
Cell B1 could be controlled using data validation, so that only "Yes" or "No" can be entered.
Put Yes in F1 and No in F2
Select B1, from the menu select Data - Validation ...
Under the 'Settings' Tab select List from the 'Allow:' box.
Then in the 'Source:' box, select cells F1 to F2
Now select Cell B1 and it will have a drop-down with Yes and No in it.