Comparing slope of two regression lines

[MattK]

I want to determine if the the response to one treatment is different from another.  I have multiple animals, some that received drug A and others drug B.  They are distrubuted based on starting weight, so the x-axis is a continuous variable.  The y-axis is response time in seconds.  Essentially I would like to determine whether the slopes of the best fit lines are similiar or different.    

[trekvana]

build a linear model y= intercept+x+trt +x*trt and then test the coefficient for x*trt to see if the slopes are zero. to test if both treatments have the same intercept then test the trt coefficient to see if it zero.

[MattK]

Is there not a way to perform this analysis without writing script?

[Doc_Duke]

you can do it in the point-n-click interface of Enterprise Guide.