Just make sure you don't access any properties of a form outside the forms code.
To get data from one dll to another you can pass variables as parameters between them, same as you can pass between modules or procedures within one app.
Example for passing parameters in a one app situation:
VB Code:
Private Sub commandbutton1_click()
Call first
End Sub
Sub first()
Dim strBla As String
strBla = "Hello I made it to the other sub!"
Call second(strBla)
End Sub
Sub second(ByVal strMsgString As String)
MsgBox strMsgString
End Sub
You can place both subs in one project or in two dlls. will work the same.
hth,
Helger