This is one area unfortunately where WordPerfect beat Word hands down :-(. Despite having the perfect vessel for it for over 5 years (the content control), Microsoft has yet to provide a functional "change" event to perform this function:
(CC1 content = 1 + CC2 content = 1) = CCSum content = 2
Change CC1 content to = 2 and CCSum content should automaticall change to = 3
You can get close with the methods shown here:
http://gregmaxey.mvps.org/word_tip_pages/content_controls_use_in_math_operations.html
but to do so, you must first "Exit" the variable CC.
You can even make it automatic using a custom change event but it is complicated and involves a lot of overhead:
http://gregmaxey.mvps.org/word_tip_pages/content_control_custom_events.html
Hopefully one day MS will fully realize and exploit the capabilities of CCs.
All that said, you do have to update the field. But you don't "have to go there." I don't know what type of fields you are using, but you might be able to use the exit event from the fields, or simply toggle to print preview which should update fields.
