Quick reply...
So, a Calculator-Based Laboratory can send data to a calculator, from CBL's serial port to calculator's mini-B USB port. Right? I don't know the shape-appearance-structure of CBL's serial port. However, I expect there is an easy-to-find micro-mini USB adapter. You will need it because N900 has micro-USB port, and the TI's cable for connecting CBL with calculator expects a mini-B-USB port.
That's all I can say about hardware. Now, software...
Usually, N900 receives power through the port, from either a charger or a computer. However, in order to connect to USB based data collection devices and probes, like some TI-calculators do, N900 needs USB-On-The-Go.
There is a beta hostmode on N900. It is Beta software but has been proved to work by numerous people on here... For example, by attaching a USB mouse to N900.
There is a thread for problems with specific peripherals.
Best wishes.
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Per aspera ad astra...