structure

how to declare a structure/class in vb?

Those are two different things.

A structure in VB is called a "User Defined Type"
A class can be created by adding a class file.

Those are two different things.

A structure in VB is called a "User Defined Type"
A class can be created by adding a class file.

ok, but can you give me an example of a declaration of such "user defined type"

You declare the type in general declarations:

Private Type Cat
Name As String
Weight As Integer
End Type

And use it on your form/module:

Dim aCat As Cat
Dim anotherCat As Cat

aCat.Name = "Boots"
aCat.Weight = 7

anotherCat.Name = "Bill"
anotherCat.Weight = 8