So I want to use this microphone both for skype and for my general audio recording purposes, but it is really sensitive (not exactly a bad thing). Is there a way I can set it up so that it picks up sound only louder than a certain decibel value?
Aren't Cherry MX Blues practically designed to be loud? I heard once that DasKeyboard used to offer ear plugs as an accessory (as a joke)...
I love my mechanical keyboards, but I use MX Browns any time there's going to be a mic in use (like for videoconferencing. Obviously I don't use a keyboard at all when I'm recording something important.) That said, the answer to your question is yes, you would use something called a noise gate on your input. You can read the Wikipedia article, but it basically kills the signal until the input is above a certain threshold, with some other parameters for response time.
The caveat to this is that, first, your level of speech must be ABOVE that of your keyboard, and second, when your mic is on because you're speaking into it, it's still going to pick up the sound of the keyboard if you happen to be typing at the same time. It's not a filter.
BUT, let's talk about filters! In my experience with MX Blue keyswitches, the sound they make tends to be very high in pitch. You might consider recording the sounds that your keyboard makes, and running an FFT to determine which frequencies it is loudest at. Then, you could run your signal through a filter or EQ that would "zero out" those frequencies. This only works if the keyboard frequency band is relatively well-contained -- if you zero out too much bandwidth, you'll significantly affect the sound of your voice going through the same filter.
I also have a Blue Snowball Mic and a keyboard with Cherry MX Blue switches. Getting rid of typing noise seems straight forward if you are either typing OR talking. But filtering out the typing while speaking would take quite a bit of effort and could also result in taking away sound that you want to hear that is part of your voice.
For me the best solution would be to make sure that your voice is much louder then the keyboard. That way when listened at normal volume levels the keyboard sounds would very low level background chatter. So turn up the sensitivity to your mic and talk really close to it while keeping your keyboard as far away as you can with your setup. Maybe keep the keyboard on your lap while while the mic is elevated on your desk.
The type of keyboard you have is usually for people that are gaming or spend a lot of time writing. If you are serious about recording then you must use a quieter keyboard or avoid the keyboard altogether. If you see all the great recording studios they use a lot of soundproofing and they do everything they can to make sure any unwanted sound doesn't reach the microphone before any processing takes place.
Although you technicaly can't set a microphone to ignore all sounds below a certain level, there is a tool you can use, and it is called a noise gate. What it does is it silences all audio below a certain threshold(say -20dB). Thus, assuming your microphone is close to your mouth(closer than the keyboard) you can set it up so only audio passes through when you're speaking. Then, you could apply some gentle EQ around the high mids(700-2000 Hz, I don't know the exact frequency of the Cherry Mx Blues)
The obvious drawback is that you'd have to post-process your audio in something like Pro Tools, but it isn't really hard to do anyway. Hope to have helped(if you have any doubts, look up noise gate or eq, you'll find them instantly)
Sorry, person above me said pretty much the same thing. Still helps to have another opinion though.