Confidence for pooled within group slope

In SPSS simple linear regression one can get the confidence limits either side of the linear regression slope simply by ticking the "prediction interval" box in SAVE. The upper and lower curvilinear bounds along the slope are then saved as columns with the original data.
I want the equivalent for the pooled within-group slope thats associated with ANCOVA in GLM univariate. Can anyone tell me how to get this? I also have BMDP but its not apparent to me how to get the info from this program either.
There is a difference between a prediction interval and a confidence interval. Which do you want?
In SPSS-analyse-linear regression-SAVE the box is entitled "prediction interval" and the checkbox inside this where you select the level, eg 95%, is called "confidence interval" . Thats why I quoted those terms. What I want is the 95% confidence limits either side of the slope in the XY plot.