One way:

Public Sub CommandButton1_Click()
Range("A3").Value = Range("A1").Value + Range("A2").Value
End Sub

In article ,
"Dr.H.Subramanian" wrote:

How can I add values in 2 cells using a command button
Example - Values in A1 and A2 to be added and shown in A3 at the click of a
command button (ADD) which is inserted from the tools box.