ListView checkboxes and spacebar

I have listview with checkboxes. When the listview is selected, and user presses the Spacebar key, the selected item gets checked / unchecked. Listview does this.

But when user presses Alt + Spacebar, the item also gets checked / unchecked, AND the application menu is displayed too. I do not want the item to get checked if user presses alt  + spacebar. How do I do that? Checkboxes, for example, work fine, but listview has this bug. I use the version 6 of common controls.

Also please note that pressing Alt, releasing it, and pressing spacebar after that also opens the application menu normally. This behavior should be preserved. But anything is better than nothing, so all answers are appreciated.
JiriNovotnyAsked:
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danaseamanCommented:
Looked at some code and found:
VbSpace w/o Alt toggles check status via WM_KEYDOWN.
You can disable the checking by using ISubClass_WindowProc = 1 in lieu of ISubClass_WindowProc = CallOldWindowProc(hwnd, msg, wParam, lParam), however this does not disable the Alt+VbSpace which appears to be handled internal to ComCtl32.Dll.

You need to subclass the control and monitor message LVN_ITEMCHANGING and when there is a state change AND ShiftState = vbAltMask then just cancel the change. This is actual code for modified VbAccelerator ListView that fixes this problem.

            Case LVN_ITEMCHANGING
               
               ISubClass_WindowProc = CallOldWindowProc(hwnd, msg, wParam, lParam)
               ' Editing the state of an item
               CopyMemory tNMLVOD, ByVal lParam, Len(tNMLVOD)
               bOldState = (tNMLVOD.uOldState And LVIS_STATEIMAGEMASK) = &H2000
               bNewState = (tNMLVOD.uNewState And LVIS_STATEIMAGEMASK) = &H2000
               If bOldState <> bNewState Then
                  iShift = pShiftState()
                  Debug.Print "bOldState <> bNewState", iShift
                  If iShift = vbAltMask Then
                     ISubClass_WindowProc = 1 'Cancel the change
                     Debug.Print "Disable Alt+Space"
                     Exit Function
                  End If
               End If

If you wish to do this to the Vb ListView just add a suitable subclass component and take over control of LVN_ITEMCHANGING as shown above.
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JiriNovotnyAuthor Commented:
Thanks for your great answer.

I want to do this for standard VB6 ListView. For some reason, subclassing doesn't work:

AttachMessage Me, lvTasks.hWnd , LVN_ITEMCHANGING

I do not receive any messages. I use SSubtimer6 from VbAccelerator
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Visual Basic Classic

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