How to change message v1 501 to be an error message ?

Hi guys,

When i use VA01 creating a sales order reference to contact, if sales order's quantity is larger than contact's quantity, the system gives an warning message :

Target qty of reference: 100 PC (total referenced: 101 PC)

Message no. V1501

I can't find V1 501 with tcode OVAH , anyone knows how to change Warning to Error for this message?

Thanks.