ok, by the look of your Sub you just wrote that on your own. if you
doubleclick on the button in design mode it should create the Sub for you
that will look like
Private Sub CommandButton3_Click()
otherwise you can go to the IDE (where you type the code) and you should see
two drop down menu's, click the left one and select CommandButton3, the right
combobox should automatically populate with Click and you should see this
Private Sub CommandButton3_Click()
End Sub
add your code in there like this
Private Sub CommandButton3_Click()
CommandButton3.BackColor = RGB(0, 0, 100)
End Sub
let me know if you still have trouble