>When a new grid is created, by default it columns contain textboxes.
>How can I replace in several columns a textbox with a checkbox?
>

This is all much easier if you use the Toolbox instead of the Form Controls toolbar. Check out reason 1b in this paper:

http://www.tomorrowssolutionsllc.com/Conference%20Sessions/Top%2010%20%28or%20more%29%20Reasons%20to%20Use%20the%20Toolbox.pdf

Tamar