How Can I Override the Processing After a Change/Add?
If you need to intervene in the processing after the system successfully completes a Change or Add operation, define the function privatePostChangeSucceeded() or privatePostAddSucceeded() in your TabMenu user exit file. The function should return a boolean to indicate whether the system should refresh the UI with the newly returned server data. You'd want to return false if e.g. you navigate to a different TabMenu.
Example :

function privatePostAddSucceeded() {
    var model = parent.model;
    var modeFlag = model.getValue('COMPL_NAV_MODE_FLG');
    var navKey = model.getValue('COMPL_NAV_KEY');
    var complSw = model.getValue('CMPLT_CLICKED_SW');
    if (complSw && model.getValue('ENRL_STATUS_FLG') == '30') {
        if (modeFlg && navKey){
             if (modeFlag == 'G') {
                parent.tabPage.gotoContext(navKey);
                return false;
             } else if(modeFlag == 'A') {
                parent.tabPage.addContext(navKey);
                return false;
             }
        }
   }
   return true;
}