How to trap Left Click in Excel? - excel

Question

I want to know if the selection of a cell is caused by a cursor move or by a mouse action.
There are a lot of articles explaining how to trap mouse click in Excel, even some explaining that left click can be trapped.
This code is found many times on the web:
' The declaration tells VBA where to find and how to call the API
Private Declare Function GetAsyncKeyState Lib "user32" (ByVal vKey As Long) As Integer
' The function returns whether a key (or mouse button) is pressed or not
Public Function KeyPressed(ByVal Key As Long) As Boolean
KeyPressed = CBool((GetAsyncKeyState(Key) And &H8000) = &H8000)
End Function
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
If (KeyPressed(&H1) = True) Then
MsgBox "Left click"
End If
If (KeyPressed(&H2) = True) Then
MsgBox "Right click"
End If
End Sub
This code traps the right click event, but not the left! Probably because it is placed in the Worksheet_SelectionChange event which is only called when a SelectionChanged has occurred and therefore when the left button has already been released!
How to detect a left click on a cell of a sheet to know if the selection of a cell is caused by a keyboard input (arrows or enter) or by a mouse left/right click action?

Answer 1

I found this great article and adapt it for mouse button check : https://www.mrexcel.com/board/threads/keypress-event-for-worksheet-cells.181654/
Add this module:
Option Explicit
Declare Function SetWindowsHookEx Lib "user32" Alias "SetWindowsHookExA" _
(ByVal idHook As Long, ByVal lpfn As Long, ByVal hmod As Long, ByVal dwThreadId As Long) As Long
Declare Function CallNextHookEx Lib "user32" _
(ByVal hHook As Long, ByVal nCode As Long, ByVal wParam As Long, lParam As Any) As Long
Declare Function UnhookWindowsHookEx Lib "user32" (ByVal hHook As Long) As Long
Declare Function GetActiveWindow Lib "user32" () As Long
Declare Function FindWindow Lib "user32" Alias "FindWindowA" _
(ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Const HC_ACTION = 0
Const WH_MOUSE_LL = 14 ' Type of windows message to be hooked
Const WM_RBUTTONDOWN = &H204 ' Mouse message for right button down
Const WM_LBUTTONDOWN = &H201 ' Mouse message for left button down
Type KBDLLHOOKSTRUCT
vkCode As Long
scanCode As Long
flags As Long
time As Long
dwExtraInfo As Long
End Type
Dim hkLowLevelID As Long ' Hook id of the LowLevelMouseProc function
Dim LeftMouseDown As Boolean ' Flag to trap left mouse down events
Dim RightMouseDown As Boolean ' Flag to trap left mouse down events
Dim EllapsedTimer As Date
Function LowLevelMouseProc _
(ByVal nCode As Long, ByVal wParam As Long, lParam As KBDLLHOOKSTRUCT) As Long
On Error GoTo ResumeHere
' CAUTION !!!
' We can't do any action which envolves UI interaction because Excel is already beeing to update UI
' Hook mouse events only if XL is the active window
If GetActiveWindow = FindWindow("XLMAIN", Application.Caption) Then
If (nCode = HC_ACTION) Then
' Check if the left button is pressed
If (wParam = WM_LBUTTONDOWN) Then
LeftMouseDown = True
EllapsedTimer = Now() + TimeValue("00:00:01")
Application.OnTime EllapsedTimer, "ResetFlags"
ElseIf (wParam = WM_RBUTTONDOWN) Then
RightMouseDown = True
EllapsedTimer = Now() + TimeValue("00:00:01")
Application.OnTime EllapsedTimer, "ResetFlags"
End If
End If
End If
ResumeHere:
' Pass function to next hook if there is one
LowLevelMouseProc = CallNextHookEx(0, nCode, wParam, ByVal lParam)
End Function
Function isLeftMouseDown()
isLeftMouseDown = LeftMouseDown
End Function
Function isRightMouseDown()
isRightMouseDown = RightMouseDown
End Function
' Reset the flags if the click has been thrown too long ago
Sub ResetFlags()
RightMouseDown = False
LeftMouseDown = False
End Sub
' Call this proc when opening Workbook
Sub StartHook()
If (hkLowLevelID = 0) Then
' Initiate the hooking process
hkLowLevelID = SetWindowsHookEx(WH_MOUSE_LL, AddressOf LowLevelMouseProc, Application.Hinstance, 0)
End If
End Sub
' Call this proc when closing Workbook
Sub StopHook()
If hkLowLevelID <> 0 Then
UnhookWindowsHookEx hkLowLevelID
hkLowLevelID = 0
End If
End Sub
It defines 2 procs StartHook and StopHook that you use in "ThisWoorkbook":
Private Sub Workbook_Open()
Call StartHook
End Sub
Private Sub Workbook_BeforeClose(Cancel As Boolean)
Call StopHook
End Sub
And 2 functions that you can use in the macro for the Sheets like this:
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
' Check if the mouse Left button was pressed
If (isLeftMouseDown()) Then
... do some stuff on left click - for example ...
If (ActiveCell.Column = 1) Then
MsgBox "You LeftClick in column A"
End If
...
End If
End Sub
Caution :
The flag can be read for 1 second after the click event, they are then reseted. That is to prevent some side effect when leaving excel and coming back to it.

Answer 2

Addendum to the code answer:
As of VBA 7 and above, the 'Declare' statements at the beginning need to also include 'PtrSafe'. Microsft added this check to ensure that the 'Declare' statement is safe to run in 64-bit versions of Office. See the article here:
https://learn.microsoft.com/en-us/office/vba/language/concepts/getting-started/64-bit-visual-basic-for-applications-overview