help please

Hi all,
my first time here so i hope this is the right place to post.

I'm trying to make a DB for a music project with Creator. I have created a form from the scratch where i build the line myself by the help of the builder at left side of screen.

Now what i want to do and can not figure out how is this:

I have a dropdown line called Section. And next field is Type.
What i want to do is, when you click the Section then The Type will automatically show you the choices within that section. But how do I do it?

Exp. Section has A,B,C
Type has 1,2,3, ect.
When you choose section A then 1,2,3,ect shows automatically.

i hope its clear enough and someone can help a bit.
Thanx in advance
cheers