how to read data from weighing bridge machine

Question

.currently m working on a weighing bridge software .currently our client has a old weighing machine (nearly 8-9 years ).n they want to upgrade the software .the problem is that i need to read weight of any truck from tht old machine which is connected to pc into a text box in window application .i have no idea how to do that .n here is none to help me .

pls solve my problem and tell me the solution  in a step by step manner .


thanks in advance.