sed how I can replace csv only IF line contain string? : <p>I have a csv like this</p>

<pre>
titlemmmm;fff;ggg
mmmm;fff;ggg
mmmm;fff;ggg
</pre>

<p>I need to replace for obtain this</p>

<pre>
titlemmmm*fff*ggg
mmmm;fff;ggg
mmmm;fff;ggg
</pre>

<p>how I could do this </p>

<p>Please help me</p>
