How do I click a button that does not have a shortcut assigned to it?

First try to see if you can Tab to the button and then press the Enter key to simulate the mouse click.

Or try the Window Control commands. The tutorial in the help file goes through an example of this. Macro Express can look for window controls, such as buttons, edit boxes, window titles, etc. and take action on the controls. So you could instruct the macro to click on a specific control (button in this case).

If the button in your application was not created as a window control, then try the Mouse Move – Relative to Window command. With this command you specify where to move the mouse based on its position in the active window. As long as the field you are attempting to move the mouse to is still visible on the screen, and as long as it is always in the same position from the upper left corner of the window, this will work.