Finding Significant Difference between Linear Regressions


I have a scatterplot with two different sets of data plotted. Each individual set has its own linear regression formula and R-squared value. What type of test could I run on Microsoft Excel to get a p value to see if one dataset's trend is significantly different than that of the other dataset?

Also, what would be the best method to identify/calculate outliers, if they indeed need to be removed to show significant difference?