Instance name inside DataGrid

I have a small problem related to the instance names of the variable.
I have my DataGrid named “grid” dragged in first frame
In AS I wrote
I get _level0.grid as output
Now when I go to the 10th frame and do the same
Flash says its undefined
Is there anyway I can access the grid from 10th frame as I need to add data to grid only from 10th frame
Many thanks!