Hi Malc,
My VB is very rusty at the moment but have a look at the Split function in VB. It can be used to split a single string into separate strings (an array of strings actually) and you can specify the delimiter used. So if you send your values as text (which you are at the moment) separated by a comma you can use split the recived string into separate strings which you can the us to populate the textboxes.

If your string as read from the serial port object (let's call it RxString) looks like:
002610,002660,002680,002680
Then something like MyArrayOfStrings = Split (RxString, ",") will return 002610 in the first element of MyArrayOfStrings, 002660 in the second and so on. You can then do something like myTextBox1.Text=MyArrayOfStrings(0)

This is all untested but lookup Split in MSDN and string handling/parsing in general.

/Henrik.