1. View | Toolbars | Customize
2. On the Commands tab, click Macros on the left-hand side
3. Drag the appropriate macro to the standard toolbar (say, next to the “Send/Receive“ button)
4. Right click on the button and change the Name field if you want to shorten the text or assign a different accelerator key
5. Click Close

Now, any time you click on that button, it will execute the macro you selected.