Slicing objects

Hello:
I am having a problem with slicing objects (vector images). I don't know what the trick is, but in the old days (Micrografix Designer), I could just draw a line through an image, and slice on that line. I know that was a long time ago, and I have been functioning without it for years....but it would sure make life easier. With Corel Draw and Designer; no matter how many ways I try, I can not slice an object. I have tried the knife tool (which I find awkward anyways). I have done everything according to their help files....things just wont slice (bisect).
Any help would be appreciated.

Thanks
Ben

In Illustrator... Draw a line on your object(s) and select Divide Objects Below (Object > Path > Divide Objects Below). This will divide all the objects below that line.

or

Draw a line on your object(s), select the line and the object(s), and select Divide from the Pathfinder panel (bottom left). Ungroup.