I want to see if the intercepts and slopes of two linear regression lines are significantly different. I thought I found the solution but now it looks like that might not work because the data is overlapping. Specifically:

I have data for X, Y1, and Y2. I can find the regression for both (X,Y1) and (X,Y2), and determine whether those are significant. But now I want to test whether the intercept/slopes are different between the two regressions. Alternatively, I could test whether they were the same a 0/1. Mainly, I'm interested in the intercept, if say 3 and 5 are different, given the variances of this data. The slope is ~1 for both and r is very high (>0.98) for both.

Is there any way I can test this significance? Either using the raw data or given standard errors etc.? Information about this in linear regression is appreciated, as well as higher order regression (but not as crucial and might be less meaningful). Also, I don't know if ANCOVA/MANCOVA is appropriate or how to implement that. I can do this mainly by hand/Excel, SPSS, or MATLAB (R etc. I might be able to translate).

Much appreciated.