Form Personlizations on Price Adjustment block on Sales Order Form

I want to disable Rate Field on Price Adjustments block on Sales Order form but the personalizations form doesn't work when I query it after Opening Adjustments block.If I close the Adjustments block and then try to personalize on the already opened personalizations form then it gives the error that 'The form that you were try to personalize is not open.Please open it and try again' If I try to personlize on Sales Order form then the Trigger Event doesn't show in the list of values.