You can always set the contol Visible property to True/false depending on what you want. I do this in some of my reports to output a "continued on next sheet" when I have output a certain number of lines.
Use the Format report associated with the section that contains the controls you want to hide/show.
If x = true then
me.somecontrol.visible = false
else
me.somecontrol.visible = true
end if
If you are using A2007, report controls have events so you can do the hide/show in response to the click event of a control.