Binding to CheckableCommandParameter.Tag

I've a simple Ribbon which contains a button wired up to a command that normally takes a parameter, the value of which is set via a binding:

<Button Command="MyCommand" CommandParameter="{Binding MyValue}"/>

Using a ribbon button means that it sends a CheckableCommandParameter to the command, which is fine since I need the button to be checkable anyway, however I cannot work out how to send the command the value from the binding source along with the CheckableCommandParameter.

I thought I might need something like:

<ribbon:Button Command="MyCommand">
<ribbon:Button.CommandParameter>
<CheckableCommandParameter Tag="{Binding MyValue}"/>
<ribbon:Button.CommandParameter>
</ribbon:Button>

However, it seems that it isn't possible to bind to the Tag property. Is there a way of doing something like this that I've overlooked? Or does use of CheckedCommandParameter mean that I can no longer send a value to the command via a binding?

Many Thanks

Tim Mawson
i2 Ltd.