Word 2010 - Calculations in a locked Filling in Form Template

Created a template using filling in form and I have added Bookmarks to certain cells to calculate the cost of an item, item with taxes, and grand total. When I lock the form, the calculations do not compute. Tried saving, printing, F9, nothing works. When I unlock the form and press F9 the calculations work. How do I get the calculations to work when locked?