Can anyone help me with a scroll bar problem.

I have a picture within a form which has an HScroll and VScroll scroll bars but the size of the thumb or slider isn't proportional to the missing portion of the picture.

I know it has to do with the
HScroll1.SmallChange
HScroll1.LargeChange
VScroll1.SmallChange
VScroll1.LargeChange
variables but I just don't understand them. No matter what I do to test on them it doesn't make sense.

Basically I need the variables to be a function of the form size and the picture size. ie form1.height/picture1.height

At the same time can someone explain what the difference between picture.height and picture.scaleheight?