Automatically solving for X or Y intercept on a log or exponential graph.

I am new to VB so hopefully this wont seem too disconnected.

I am trying to set up a sheet that automatically graphs, sets a fitline
and displays the X intercept value in a cell when I enter 5 or 6
datapoints.(based on the equation of the fitline)

I'm sure it's not a hard prospect, but I am not sure where to begin. I
usually have 5 or 6 datpoints times about 50 samples to graph and
determine the X intercepts for. The data usualy fit a log-line well.

Thanks,

Jed