Numbers on a Log scale graph.....

Hey,

Just wondering if anyone can help me with a little problem i'm having......
I have a graph with a log scale on the x-axis and i'm wonderinf if there is any way of having excel pick a number off the x-axis for a given number on the y-axis? Also will it still work if the graph continues to change?

Thanks

hey,

I have attached a print screen of my graph. It has percent on the y axis and particle size on the x axis in log scale. If the graph changes with new results and a automatically get the particle size for a certain percent?

Thanks