Form 112 and cs exe.

Hi all, I wanted to know for CS Executive Registration do we first have to fill the form 112 with ICAI first (since I am doing Articleship) or can we submit that form 112 even after registering with the CS Institute. Becasuse the last date for CS Excecutive Reg to be eligible to write in Dec 12 is May31st. So could you please help me on this.