Option Explicit
 
Private Declare Function GetTickCount Lib "kernel32" () As Long
Private Declare Function GetLastInputInfo Lib "user32" (plii As Any) As Long
 
Private Type LASTINPUTINFO
    cbSize As Long
    dwTime As Long
End Type
 
Private Sub Timer1_Timer()
    Dim lii As LASTINPUTINFO
    lii.cbSize = Len(lii)
    Call GetLastInputInfo(lii)
    Me.Caption = FormatNumber((GetTickCount() - lii.dwTime) / 1000, 2)
End Sub