Adding custom ovs to extended field?

Hi Experts,

I have created one custom business object and created custom ovs screen. Now i have extended the standard business object(service request) with two fields in item node and adding the extended fields to the Item table of service and repair tab in service ticket screen.

It got added successfully. Now i am adding my custom ovs to the extended field in item table. But it is showing the error as showing below image.

Step1: Adding OVS.

Step2:Select the custom ovs

Step3: It is showing error, "The selected OVS may not be used by ISV". I don't what that mean.

Can anybody guide me.

Many Thanks,

Sree.