I need to be able to select one of 2 cells with a double-click, like a switch

[chrisneu]

My sheet is used to extract numerical values to column B from the pasted text into column A, and columns D, E, and F are used to add, subtract, or to multiply the entered values by selected percentage. Column C is used for alternative values, which are entered directly into the cells in the column. User then selects the column, either B or C, the values of which to be processed in D, E, and F, by double-clicking either the cell B2 or C2. However, I have a few problems with my sheet:

1. Cells B2 and C2 should function as "either-or" selection: double-click on B2, should put a bullet into the cell and clear the cell C2. Double-clicking C2 should put the bullet into that cell and clear the B2.
2. When empty, like the A6, columns D, E, and F should remain empty (unlike now as "#VALUE!" is displayed in D6, E6, and F6)
3. It has been working for me as it is, but it would be nice if D3, E3, and F3 were displaying decimal points: currently, they all display "2500" whereas it really should be "25.00". The problem is that the adjustment controls only allow integers and I was unable to get around it.

Thanks all in advance!