Show or blank out a cell dependant on an selection in another cell
 

I am creating a model where a user can select a parameter in cell A1, in this
case either "Secure existing business" or "New business".

Dependant on the answer in A1 the user should enter a number in either cell
B1 (secure business) or C1 (new business), i.e. a revenue number where the
value 0 have been pre-entered.

Is it posible to get the two input cells formatted in a way so B1 is blanked
out and appears as a non input cell when "New Business" is selected (only C1
would appear as a input cell) and opposite.

Hiding columns is not an option. Have tried conditional formatting and any
other functions I cound think of, without any success.

Sorry if this have been covered before but can anybody help here?

Regards, Lars