flex validator, checking custom conditions

Is there a way to add a custom condiiton to the NumberValidator.
I would like it to check if xmax is greater than xmin otherwise I want the validation to fail and the border around the input field to highlight in red like is usually done when validation fails.
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<mx:NumberValidator 
    	id="xminV"
    	source="{xmin}"
    	property="text"
    	invalidCharError="input error"
	/>
 
	<mx:NumberValidator 
    	id="xmaxV"
    	source="{xmax}"
    	property="text"
    	invalidCharError="input error"
	/>