How do I capture user input as a dim with VBScript?

First a little background:
1. I'm using VBScript to create custom documents for a program we're getting ready to roll out.
2. I have to use Word to create these documents.
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I'm working on creating a custom calculator to figure loan rates on construction loans. It's been smooth sailing with all the scripts and functions pre-created by the vendor, but I've hit a snag.
I'm trying to create a script that will take the user's input from an empty line as a dim to be used in a calculation later in the document. Any ideas?

Thanks in advance for your help!