App.PrevInstance [resolved]

[CVMichael]

OK, I have 2 forms, the main one I want it to show only once, and the other as many times as you run the program, but it always showing either one or the other (in the same instance).

The problem with the next code is that when I run the program with a command i.e. the frmRestore is showing, the next time I run the program without the command, the main form does not show up, and I want it to because there is no previous instance of the main form.
If I do it the other way around, then it works. If I close all instances of my program, run it without a command, then run it with a command, then it works.... get it ?

Private Sub Form_Load()
    If Command <> "" Then
        Load frmRestore
        Unload Me
        Exit Sub
    End If
    
    If App.PrevInstance Then End
End Sub

Reading what I wrote, it still seems a bit confuzing. I'll try another way...
So... I have 2 forms, main form and frmRestore, when I run the program more than once, I want the main form to show only once, but the frmRestore more than once, and it should not matter in witch order I run them, main form should always be once...

[imbue]

Could you make two different apps? Then each app would of course have its own App.PrevInstance. If the main form wants to load up and it's already loaded it could just shut down, regardless if the frmRestore is loaded. If you pass it a command it could just shell the frmRestore program.

I hope I understood your question correctly.

[CVMichael]

The program is ~6000 lines, and both forms have a lot of common code, making 2 apps would create a lot of problems.

[CVMichael]

I fixed the problem using some APIs...

Private Declare Function GlobalAddAtom Lib "kernel32" Alias "GlobalAddAtomA" (ByVal lpString As String) As Integer
Private Declare Function GlobalDeleteAtom Lib "kernel32" (ByVal nAtom As Integer) As Integer
Private Declare Function GlobalFindAtom Lib "kernel32" Alias "GlobalFindAtomA" (ByVal lpString As String) As Integer
 
Private Const MyAtomName As String = "MyApp12345"
Private CurrAtom As Integer
 
Private Sub Form_Load()
    Dim Atom As Integer
 
    If Command <> "" Then
        Load frmRestore
        Exit Sub
    End If
 
    If App.PrevInstance Then
        Atom = GlobalFindAtom(MyAtomName)
        If Atom = 0 Then
            CurrAtom = GlobalAddAtom(MyAtomName)
        Else
            End
        End If
    Else
        CurrAtom = GlobalAddAtom(MyAtomName)
    End If
End Sub
 
Private Sub Form_QueryUnload(Cancel As Integer, UnloadMode As Integer)
    GlobalDeleteAtom CurrAtom
End Sub