<span style="color: lightblue">Can I edit an existing file using VB ?? If so, what is the syntax ??
And can this be used to add code to an existing form ?? How would I specify what sub/function it goes in ??

You can open a file for reading or writing. To edit it, you would have to read it in, edit, then write it out again.

But if you want to write self-modifying code VB is a very bad choice. Any compiled language is a bad choice of course. You would need to open the file in binary mode and edit the actual op-codes. And those op-codes arent intel-standard like you can look up on the net, there M$ pseudo-code that runs through a virtual machine. And no-one has the complete list of op-codes. Plus compliers do funny things to functions - the code wouldnt be organised anything like what you originaly entered.

Add to that the fact that you wouldnt be able to open the file while windows has it open for execution.

So no, you cant write a program to add code to a form.