I have managed. I first defined the column:
<th field="pur_received" width="20" formatter="showButton">Action</th>
And then rendered the button if the criteria was met.
function showButton(val,row){
for(var name in row){
if (row["pur_received"]=="Received")
{
} else {
var s = '<button class="easyui-linkbutton" iconCls="icon-edit" onclick="receive_goods(this)"></button> ';
return s;
}
}
}