Hello. Sorry if this has been asked before, but I can't find how to do it anywere.

The problem is the following:

I need to be able to autofill a drop-down list if some cell is not empty.

To be more clear, suppose that i have a drop-down list
in cell B1.

Now, suposse that cell A1 can have a catalog code A, B, or P, or be empty. If it's empty, I want B1 to be the drop-down list, else to be the item specified in A1.

I've narrowed to this:
and in the Data Validation Box, under "Source" I've the following
This works well, except the drop-down shows an empty cell and one has to manually select Apples or Bannanas or Pinapples, wich defeats the whole purpose.

Any suggestions so cell B1 is automatically filled when A1 is specified, or a drop-down if not?