Counting the number of open window using VB.

I've written a program, and part of it needs to cycle through every open window on my PC (doing a Alt+tab sendkey) only once. Anyhow, I need to know how I can get a count of the number of open windows on my PC, so I can use that as a comparison value in a FOR statement. Is there a function that returns this value? Thanks,

Joe

....
Private Sub Command1_Click()
dim windowCount as integer
dim i as integer

windowCount = <function that returns number of open windows>

For i = 0 To windowCount
... do stuff...
Next
End Sub
....

I'm using Visual Basic - Microsoft Visual Studio 6.0

It's much easier to use:

Declare Function EnumWindows Lib "user32" (ByVal lpEnumFunc As Long, ByVal lParam As Long) As Long