Refering to General Question

Does anyone know how to differentiate the cell formed by a value or a formula?
such as in cell a1 = 7 [value only] and in cell b1 = 3 + 4 [any formula]
If the cell contains value, then return 0, else
If the cell contains formula, then reurn 1.
In this case, a2 = 0 [return], because a1 contains value and
b2 = 1 [return], because b1 contains formula
Does anyone have any suggestion?
Thank you in advance
Eric