What is not working  about it? Other than it won't perform
simultaneously? The code will run one command after another.

Are you getting error codes? What is the name of the subroutine? Is it
Sub commandbutton1 () or is it Sub commandbutton1_Click() ? In which
case try:

Public Sub Combined()
Commandbutton1_click
Commandbutton2_click
Commandbutton3_click
End Sub