Two separate check boxes affecting the same fields

Hi all,

I have 2 check boxes 1-Group8.c0 and 1-Group8.cf each with 5 further check boxes.  If the boxes (.c0 & .cf) are checked the relating 5 check boxes should be hidden, if left unchecked the relating 5 check boxes should remain visible for use.

I have the following code in the mouse up event of each check box

In Group8.c0

if (this.getField("Group8.c0").isBoxChecked(0))
{this.getField("Group8a").display = display.hidden;}
else
{this.getField("Group8a").display = display.visible;}

In Group8.cf

if (this.getField("Group8.cf").isBoxChecked(0))
{this.getField("Group8b").display = display.hidden;}
else
{this.getField("Group8b").display = display.visible;}

When checking Group8.c0 the fields named Groupa become hidden, however if i then check Group8.cf, Groupb become hidden and Groupa become visible.

Could someone please shed some light as to what i have done incorrectly