Microsoft Word comes with everything you need to create a Table of Contents (TOC) that updates automatically.

Start with formatting a Heading1 and Heading2 Style

These styles already exist in word.  Customise these to your corporate look and feel, then apply them to you headings.

Add a Table Of Contents from the Refences tab

Again Microsoft have provide a default options under References > Table of Contents.  It is possible to customise the format the TOC through the TOC1 and TOC2 styles.

<F9> Updates Your Table of Contents

Update your document, add more content, change headings.  To update your TOC, click on the TOC and press F9.