I have 3 fields in excel as follows:

Cell **A1=2012 A2=12 A3=15** which contains year, month & date value respectively. And I want to make a date string out of it.

I know it's very easy to achieve using Date() function.
**But I also want the cell to remain blank if any of A1,A2 or A3 is blank.**

Anybody has a formula/logic for this?