When doing state income tax forms you have to enter your federal income tax refund received that year.?

When filing Married filing separately (as I am) it says, "If the refund received was from a jointly-filed federal return (which it was) it must be divided between the spouses in ratio of the spouses' net income in the year for which the refund was issued. How do I do this. For instance if our refund was $7,034 and I have to claim that on my state tax form how do I split that up between the filer and his spouse? How do I find this ratio?