How to draw a self message in msc package to another action box only rather than the axis itself?

I want to draw a picture like this with msc package.[1]
I want to draw a self message which will not touch the self axis rather it will touch only the outside(left) of an action box, please help me in this regard. Thank you in advance.

I am giving my code below:

begin{msc}{}
declinst{a}{{A}}{}
mess*{{Include a particular value}}{a}{a}[2]
nextlevel[1.5]
action*{{Generate Values}}{a}
nextlevel[1.5]
end{msc}

This is what I want:
[1]: https://i.stack.imgur.com/NBExe.png