Problem in saving my MS Excel files created from the earlier version

I have a problem in saving my MS Excel files created from the earlier version 97-2003 to the newer version which is 2007. Sometimes when I do this, some formula will not work properly. A notification appears that some of the formulas and data will not update will not be updated. How will I solve this problem?
Is there a button I should click so that the whole file will work?
