You should have gotten the checkbox in the grid by:
1) Right click on grid, then select EDIT
2) Select checkbox from Form Controls
3) Place checkbox in grid on the column that will use it...if needed, create a new column ahead of time to place the checkbox in.

Then,
4) Select the column the checkbox was put into.
5) Go to property CurrentControl and select the checkbox control.
6) To change from always displaying the checkbox in the grid for rows that are not selected, change the Sparse property.
7) Make sure to put the full field name for ControlSource for both the column and the checkbox.

This should be enough to enable the new control; let me know if it's not working and I'll send you a form with an example.

Victor