Margin of error calculations in excel

[sakstrup]

If anyone can help, I would be most appreciative. I am trying to
figure out how to calculate margin of error in excel. Actually I am
trying to use excel to determine both of the following assuming a
confidence level of 95%:

1) What sample size do I need to survey if I know the overall
population and confidence interval?

2) What is the confidence interval if I have a given overall
population and sample size of my survey?

Thank you!