Add Interface to QTextDocument to add Undo Commands to previous stack

I would like my custom QSyntaxHighlighter to be able to change QTextBlockFormat properties such as indent, margins, line height, etc. The syntax highlighter can modify the Block Format fine through the QTextCursor interface, but this makes undo/redo not work. I would like an interface to QTextDocument to 'pause' undo, causing all new changes to be appended to the previous undo command stack.