To activate
Declare the FindWindow and BringWindowToTop APIs in a form or module, then use:
Private Sub Command1_Click()
Dim hCalcWnd As Long
Dim x As Long
hCalcWnd = FindWindow("SciCalc", "Calculator")
If hCalcWnd = 0 Then
x = Shell("CALC.EXE", vbNormalFocus)
Else
BringWindowToTop(hCalcWnd)
End If
End Sub