trigger Word macro by pressing space bar (only).  Don't want to use ctrl, F key, etc.

If you use only the "space bar" as a macro shortcut, how do you intend to insert a space in your document? Every time you press the space bar, the macro will execute!

Shortcut keystrokes have to begin with Alt or Ctrl, so you could run a macro from some such combination. Not a space, though.

I have looked at the extra events that can be used by creating a WithEvents application object, but the closest is SelectionChange, which is not triggered when typing in characters.

I figure that if there is no text to replace, the macro may execute but there is no visible effect since the find part of the macro doesn't find anything.  I just go on typing.
 
I found this code, but instead of Alt + 0, what would I put in for spacebar?

' \\ Code for Module1
Option Explicit
 
Sub AddKeyBinding()
    With Application
         ' \\ Do customization in THIS document
        .CustomizationContext = ThisDocument
         
         ' \\ Add keybinding to this document Shorcut: Alt+0
        .KeyBindings.Add KeyCode:=BuildKeyCode(wdKeyAlt, wdKey0), _
        KeyCategory:=wdKeyCategoryCommand, _
        Command:="TestKeybinding"
    End With
End Sub



 ' \\ Code for Module2
Option Explicit
 
 ' \\ Test sub for keybinding
Sub TestKeybinding()
    MsgBox "We have a winner", vbInformation, "Succes"
End Sub

My find and replace function would go in module 2.

wdKeySpacebar is the answer.

Now I will put in my find and replace in module 2 instead of the msgbox.

Oops.  Need to disable keybinding after text replacement to restore normal spacebar function.  Any help appreciated.

expert comments didn't lead to successful resolution. I was able to come up with a portion of the answer I needed. Would have liked someone to follow up on what I started.