How can I pass a structure in VB?

Simple. Define it and pass! :-)

A structure is defined with "Type"

Pulic Type Rect
Left as long
Top as long
Right as Long
Bottom as Long
end type

is the standard definition for a "Rectangle" often used in Windows API.

To pass it to a function define:

public Function someFunc( byref lpRect as Rect)
lprect.Left = ....
end function

A typical windows call would be like this:
GetWindowRect(rect1)......

Look up "Type" in Vb Help. That would be easier.

RK