Control voltage with MSComm

I'm making a IC chip tester which can detect the pin error on certain IC. This tester is connected to the pc through RS232 cable. I'm using MSComm for interfacing, but i've no idea how to send the voltages(eg 10111, 1=high and 0= low) to each of the pins on the chip tester and get the result back from the tester ??
Is it that i need to send some Hex number to control the voltages ?
Thanks in advance ......

Probably you'll need to build a circuit with a UART and supporting chips to receive the data byte from the serial line and convert it to bits.

Thanks, Doug. Yup, my circuit consists of UART. Do you know about any VB codes which allows me to send bits( which represent low or high voltage) trough the serial line?

I suppose you'd just encode the bits in a ASCII character code & then send the character serially. I don't know of any premade code for you. I'd consider encoding 4 bits per serial character so you don't have to worry about control codes & other strange stuff, all your encoded data could be printable characters so you can easily debug the program.