Or if you don't mind using string substitution, you could use
"rename":

<hansl>
function matrix myfunction (series depY, list X)
string realname = argname(depY)
rename depY @realname
ols @realname X
...
end function
</hansl>

That's cool too. Indeed I tried something similar but missed to add "@" for 'realname'...and obviously, it didn't work :)

Thank you Allin,

Artur