I am using the following formula: =IF(M5="x",W49*140%,IF(Q5="x",W49*140%,""))
but I need to change it to solve the following problem,

1. How can I use 4 cells J5, G5, M5, Q5, I need to insert a caracter into
any of this cells (at this moment I am using "x") But I really want to be
able to use any keyboard key for the formula to work.
2. using j5="x", w49*0,""
3. using g5="x", w49*0,""
4. using m5="x", w49*140%
5. using Q5="x", w49*140%
6. But the major task that I want accomplish with this formula is to allow
me to enter only one "x" (meaning I can only select ONE between J5, G5, M5,
Q5)