Formula or User Entry in single cell?

[bartonkj]

I want to repeatedly calculate 1 value or 2 values, depending on what data a user enters:
1 value -- If a user enters square feet, the acres are calculated
2 values -- If a user enters length and width, both the square feet and the acres are calculated

However, I want to do this with only 4 cells:
A1: Length - user entry
A2: Width - user entry
A3: Square Feet - user entry, or calculated number
A4: Acres - calculated number

Length * Width = Square Feet
Square Feet / 43,560 = Acres

So:
A4: "=A3/43560"

A3: "=A1*A2"

For a 1 time calculation this is no problem - if a user enters Length and Width, the Square Feet are calculated and the acres are calculated. If a user enters Square Feet, the acres are calculated, BUT it overwrites the formula in A3 such that the User cannot do another calculation to enter Length and Width to calculate both the Square Feet and the Acres.

Is there any way to allow BOTH a User to enter Square Feet and still retain the formula in A3 to calculate Square Feet from Length & Width?

Thanks.

[JohnTopley]

Simple answer is No: if overwrite a formula with data then the formula is lost.

[bartonkj]

OK, thanks. That's what I figured, but it doesn't hurt to ask if anyone knows of any esoteric tip/trick/etc....