in the example below how to scroll .b wherever pointer is placed - inside .a or .c - so outside of .b
.wrap{
display:grid;
grid-template-columns:15fr 70fr 15fr;
height:50vh;
}
.a, .c{overflow:hidden; background:orange;}
.b{overflow-y:scroll; background:lightblue;}<div class='wrap'>
<div class='a'></div>
<div class='b'>lorem<br>lorem<br>lorem<br>lorem<br>lorem<br>lorem<br>lorem<br>lorem<br>lorem<br>lorem<br></div>
<div class='c'></div>
</div>