Sending strings from defined values

My PC har to communicate with a kit. For instance, i have to write a random value of power consumption in the textbox, and send that value to the kit.

It is important for the kit to receive the values as a number, because the kit controls a "plastic made" flower, which will react dependent on the power value. So the only job i will do with C#, is to write the values in the textbox and send those values with pressing "send" button.