Here's an example Macro that should get you started.
You will need to modify to suit your requirements.
MACRO: Paste Data from Clipboard [Example]
#### DOWNLOAD:
<a class="attachment" href="/uploads/default/original/3X/9/9/9931bdc56bdb23fddc032f3d31a3060a7ee2bd9c.kmmacros">Paste Data from Clipboard [Example].kmmacros</a> (6.3 KB)
**Note: This Macro was uploaded in a DISABLED state. You must enable before it can be triggered.**
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![image|532x1217](upload://o2dQIBuS7C5Dd8Lfa0TzKDbK4Z1.jpg)
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Questions?
This is a really tiny issue and perhaps not something the OP has to worry about. Passwords can often contain special characters, including colons (where usernames are typically restricted to alphanumerics), in which case the regular expression can potentially match the wrong components of the string, e.g. "username:pass:word" matched against (.+):(.+) will return "username:pass" and "word" in the first and second capturing groups.
If that were to be a situation that arises for the OP, the regular expression can be slightly adjusted to (.+?):(.+), which will return "username" and "pass:word" as would be desired.