Storing into a coll object

Hello,

I made a little part of a patch which stores 512 values coming from a number box in a coll object with an index 0-511.

The idea is to press the space bar to enable storing and to close it when the coll is full.

It works fine excepting one thing :
The last value (511) is stored on the 1st value.

I would like to keep the same patch. I would like to know if you see a little trick to store the first value @position 0 and the last @position 511 keeping the fact that when storing is done, it closes the gate and bring the count back to 0 for the next recording.

Thanks a lot,

Mathieu