u can use KeyDown event, try like this
Code:
Private Sub Command1_Click()
MsgBox "Hi"
End Sub

Private Sub Form_KeyDown(KeyCode As Integer, Shift As Integer)
If Shift = 2 And KeyCode = Asc("A") Then 'Ctrl+A
    Command1_Click
End If
End Sub

Private Sub Form_Load()
Me.KeyPreview = True
End Sub
there r some other methods also