State tax filing

My followup question has to do with 1099-B for ETFs and Mutual funds, wherein a fraction of assets in each are US Govt. Obligations which are NJ Tax exempt.  Clicking the Omit box (if it works at all) deems the whole amount exempt, which is incorrect.  It doesn't let me modify the value for that entry to reflect the applicable part of the amount that should be NJ taxable and thus the balance tax exempt.  How to accomplish that?