simple RegEx question

[P2000]

I want to make a regex for the replace function that will replace any
"a" with "A" and any "b" with "B".

This is what I did so far... (I'm trying to learn this RegEx thing)

<form>
<input name="source" onkeyup="target.value=source.value.replace(/a/g,
'A')"/><br />
<input name="target" />
</form>

can I do it on the same replace?

Thanks!