I got a document, created by Crystal Reports. It looks like this:
John Smit
His results are:
Course 1 : 10/20
Course 2 : 12/20
Course 3 : 9/20
...
Total : 700/1000
The text in bold is variable. The number of courses is also variable.
My question is whether it is possible to replace the Crystal Reports by a Word Template? By doing that it would be possible to change the "letter" format without rebuilding the application...
You need to change your application to use external report [template, if you prefer to call it so]. This way you can change report with Crystal Reports Designer (like noted by Keikoku) and you don't need to rebuild your application.
If your application already uses external report file, then your question is not very clear to me.
I'm not sure about any Crystal Reports specific features that you may need which may make this solution a "no start", but ...
We (an Education Dept) used to use iReport and Jasper to do reporting from our Java environment, however, we found that it took a lot of developer time with all the formatting and layout of the reports. Especially if the business needs change with respect to the look of the report but not the the data, which sort of sounds like your issue here. In the end we wanted some Word solution so that the BAs could do the layout and formatting stuff on their own using Word directly. There's a few things around that help with that, but because someone knew someone who knew the developer (you know how it works) we found out about Docmosis. It works directly with normal Word documents (and open office) and with merge fields injects your data from the database into the doc. So the original docs are basically templates. The output is Word or PDF or (I think) HTML and, at least with the Word and PDFs, they look the same (we have some picky people involved in legal who care about these things).
It's a server based thing that your app would chat to across your network, but quite easy to integrate and recently there is a web service cloud version of it which is supposed to be even easier as you don't need to run your own server at all and you just call it from your app. We run our own server, but the cloud setup would be good if you have a web app or something where you don't have the option of installing it in your host environment.
Not free, but the amount of time we save pays for itself.
I'm not too sure what you mean by "letter" format and "rebuilding the application"
I don't think it would be too difficult for a crystal designer to change the font, styles, and formatting quickly.