Write a Macro, Code or an Application to replace placeholders with client logo and business details

I am a consultant and I sell MS Word templates to clients. As part of my services, I input the clients' logo and business details into the templates where I have put different placeholders such as , , , etc. I have a working Macro code. However, there are a few problems at the moment: - it takes too long to process the docs. - it stopped inputing the logo on the header. - it only works with Mac. We want it to work with Windows as well. - it has some bugs. Desired outcome: A system in Google Docs, MS Word & Excel, or a web app or desktop app which when I open the app: - Ask me about "new client" details such as logo, company name etc etc, T - Ask me the theme colour for the documents to match their logo. - Then, it changes the variables in the files all in one go. - Show the new fixed files OR Save the new files in a folder Deadline: 2 weeks