Round trip function in hcm process & forms

Hi Experts.

I am working on HCM Process & Forms using adobeforms .

I designed table as shown below .

If user selects wage type value form dropdown corresponding value of amount field should come automatically .

Please tell me is it possible to do this using round trip function & sap_pa backend service only , I don't want to use custom backend service .

Thanks & regards .

Bhushan Ghule