Refined harvard reference style

Question

I need a harvard reference style which should look like as below, except two things:

1) The 'and' between the two authors should be '&', and

2) the year should appear without the parenthesis.

Below is my simple code, which created the above result.

\documentclass[12pt,a4paper]{article}
\usepackage{natbib}

\begin{document}
    \citet{grupp1999patent} said this.

    \bibliographystyle{MyStyle}
    \bibliography{Test}
\end{document}

I tried to create and use my own reference style called "MyStyle.bst". The MyStyle.dbj file looks like as follows:

%--------------------
%STYLE OF CITATIONS:
%   %: (def) Numerical
  ay,%: Author-year
% alph,%: Alpha style, Jon90 or JWB90
% alph,alf-1,%: Alpha style, Jon90
% alph,alf-f,%: Alpha style, Jones90
% cite,%: Cite key

%--------------------
%DATE FORMAT (if non author-year citations)
   %: (def) Plain month and year
% yr-par,%: Date in parentheses
% yr-brk,%: Date in brackets
% yr-col,%: Date preceded by colon
% yr-per,%: Date preceded by period
% yr-com,%: Date preceded by comma
% yr-blk,%: Date preceded by space

%--------------------
%AMPERSAND:
%    %: (def) Use word `and'
  amper,%: Use ampersand
% varand,%: Use \BIBand

I can't find anything else to make it look like as I want. Can somebody help?