VBA Apply Font and Size to Headers and Footers

Here's the gist - File names in my workplace require basic headers and footers and I wish to create a shortcut button that will streamline these changes. To begin with - the assumption is that there is already text in the header/footer rolled forward from the prior year. I wish to press this button so that it applies the style change to the text already in the sheet. See attached file for formatting. Any help is appreciated. My current macro is setup to apply the font, but it changes the current text - this works well for new files, but not for files that have been rolled forward from prior years and simply need format adjustments.

A second question is - if I want to create a toggle button, say to show gridlines on the file sheet, is there a simple way to do that?

Again, thanks!

Note margin adjustments too.

Header left Font size 11:
Company Name
Month DD, YYYY
XXX: MM/DD/YY

Header Right Font size 11:
Workpaper Name
Page Number in work book [This cannot be static]

Bottom left Font size 9:
File: Filename [According to my macro code &9File: &F]

Bottom right Font size 11:
APX-XX