<apex:panelGroup >
<apex:inputCheckbox label="CA" value="{!BusUnits['CA']}" >
<apex:actionSupport event="onchange" rerender="BU_Options"/>
</apex:inputCheckbox>
<apex:outputLabel value="CA"/>
</apex:panelGroup>
and I want to do this
<apex:panelGroup >
<apex:inputCheckbox label="CA" value="{!BusUnits['CA']}" >
<apex:actionSupport event="onchange" rerender="BU_Options"/>
<apex:actionSupport event="onchange" rerender="BU_Codes2"/>
</apex:inputCheckbox>
<apex:outputLabel value="CA"/>
</apex:panelGroup>