Faulty Data Form

I am having trouble with a database I have set up. I am using a form for entering data and I have also uploaded data from an Excel spreadsheet. There is only one table and I created the form from a Query. Now, the problem is when I scroll on the form, through the records from the db, some of the text boxes are not updating. For instance I have some text boxes that will enter a cost depending whether a check box is checked. Sometimes the check box is checked but there is no cost listed in the text box. Also, I have a text box at the bottom of the list that is suppose to add up all the other cost in the other text boxes. Sometimes the total box does add the cost other times it doesn’t even have the default value of $0 in the box. Is there a way I can set up a check after a new record is scrolled into the form all the text boxes check for checks in the check boxes and the total box will add all the other boxes? I need help.