When entering data this can be done using the After Update event of each checkbox, where you enable the next one, for example:
Code:
If me!checkbox2 = True then
me!checkbox3.enabled = True
endif
That's OK if you only want to deal with checking a box.
But if you Uncheck it, it gets messy, because in that case you have to a) uncheck all following checkboxes and then b) disable all the following checkboxes.
You would probably also need to put similar code in the On Current event of the form, to set the proper boxes to be Enabled when you move to another record.