Hello excelforum

I have asked the question before but I need to reword it so I can find the solution that I want. I have this database table hidden, say:


Item Col 1 Col 2
Row 1 X 1
Row 2 Y 2


And I have an input in the input form in front, basically asking the user to key in the Col 1 value (X,Y,etc) and the adjacent cell will return the Col 2 value (numbers)
However, if the Col 1 input is not in the Col 1 table, (user chooses to key in, let say Z), the user has the option to put the Col 2 value independently.
The problem being, if the Col 2 value input is keyed in manually, it'll erase the formula.