Depends on the hardware. If it is modularized, and you have access to the display wiring there is a chance, if the display is driven directly from a custom processor, then unlikely.
If the data is in a serial format into a display module, then there is only a little wiring, and you would need a small micro to decode the data. if you need to access every line on the display, then there are larger problems, you would probably need to use some glue logic to process the data down to something that a uP could handle on a limited number of IO ports(7 segment to BCD). A small FPGA, muxing, or distributing the processing, one uP/digit would work. Otherwise, for a 3 digit display, for example, you would need 21 IO lines, plus perhaps spares for decimal points etc, which may be acceptable, maybe a 32 pin, probably a 44 pin uP.
If you can get the data into a micro, from there on in it is a simple matter to map the data to numbers.
Not having given any detailed information, it is in reality impossible to say.
Unless you absolutely must read it from the display, then I would suggest that another system may be the best solution.
cheers,
Richard.
