Steps for generating logarithmic (or other) regression models.

1.) Insert Chart, choose scatter point type.
2.) Enter data matrix, top row x value (Rf), bottom row y value (bp) (one can choose whether rows or columns are used for data series.
3.) Finish chart, add trend-line. Logarithmic or exponential can appear as straight lines on log paper.
4.) Right click, format trend-line, options, show equation. (Log regression model should appear in the form y = a Lnx + b where a and b are constants.)
5.) Plug values into equation by hand or typing equation into spreadsheet and cutting and pasting.

(The scatter point model is used as a means of generating this regression line because as of now I know of no way to independently enter x values in the log graph option. I generally just use my graphing calculator although the method presented here will work as well. If anyone knows how to enter two coordinate data points into log graphs on excel (not just change the name of the x values) please let me know. The problem is that the program assigns arbitrary values that are evenly spaced as x values for an entered data series, thus if your actual x values are not evenly spaced, the regression model will be inaccurate.)