cenvat credit of excise duty

as far as we know, the taxable services does not qualify any exisable input except works contract, where if composition is availed then no input credit, 

share the nature of services provided by you to discuss the matter

dear sir,

we are providing erection service. we are also deal in trading. excise duty is paid on materials purchased for trading

1) erection service comes under works contract (compositon) under service tax and WCT under VAT

2) apart from 1) what else activities you do?

3) Excise duty is not applicable on trading goods, its paid at the point of clearence of  manufacture only. 

4) under works cotract composition scheme no input credit is allowed on input materials as well as input services, and the compositon scheme allows u to pay 4.12% without input credit in place of 10.30 %