Script running on Onsave event is not saving the entity

Hi,

I've a script which will trigger when saving the Custom entity. (the script is based on one "yes or no" field, if yes after saving the entity it will open another custom entity).

But, when saving the entity, its showing the warning of entity is not saved, if I click ok on the warning it will opening the next entity as in the script. The only problem is the first entity is not saving, though I've used Xrm.Page.data.save(); in the onSave() event script.

function Opportunity()
{

var parameters = {};
Xrm.Page.data.save();

..............

.......

}