First, you need a buffer to put the characters in. You can do that like this:
char buf[32];
Of course, you will want to change 32 to a little over the maximum size of the input you're expecting.
Then, you need a variable to say what position in the buffer you are in, like this:
int bufpos = 0;
You also need some way to know when the string has been fully sent over serial. Let's use a newline:
const char EOPmarker = '\n';
and make sure to have your VB program send one!
Then you just need to read the bytes into the buffer when there's one available, and do something once you've received the EOP (end of packet) marker:
const char EOPmarker = '\n';
char serialbuf[32];
void loop() {
if (Serial.available() > 0) {
static int bufpos = 0;
char inchar = Serial.read();
if (inchar != EOPmarker) {
serialbuf[bufpos] = inchar;
bufpos++;
}
else {
serialbuf[bufpos] = 0; // null terminate
bufpos = 0;
// Do whatever with serialbuf, like print it or use the atoi function to convert to int
}
}
}