Required Checkbox Red hightlighting

I have had a problem where a grouped checkbox where only one value(checkbox) can be selected.

If a form is submitted with out any values being entered, the red boxes appear as expected highlighting all fields with a Required attribute set. However, when a check box (say 1 out 2 boxes) is selected the other check box remain highlighted in red. This implies that the other box needs to be highlighted, which is misleading.

For example Male and Female checkboxes. Submitting a form with no data highlights both boxes even though they are grouped under Sex. This misleads the user in thinking that the other box requires selection too.

I would like to know if any one has/know how to disable this group of boxes or had similar experiences.

As seen in other posting, it is required to place script behind all fields in order to remove the red box when data is eventually entered. This is the script I have been successfully using for all controls in the Validation event, except for checkboxes :
if (this.isNull)
{
this.validate.nullTest="error";
this.mandatory="error";
false;
}
else
{
this.validate.nullTest="disabled";
this.mandatory="disabled";
true;
}

When I apply this to a checkbox group the boxes no longer highlight is red, as though the ELSE statements success everytime regardless.

if anyone can assist I would greatly appreciate it. I've many things, but I would be very interested if anyone encountered similar behaviour.

Thanks
Glen