Cenvat credit taken in the excise can be utilize in ser tax?

Whether CENVAT Credit taken on excise duty can be utilised in Service tax or vice versa ?? for exapmle If I have Excise Regd. but does not have Ser Tax Regd. can I be able to take Cenvat Credit on Service Received or vise versa ?? also if i have both excise & service tax regd. how can I show this credit system in the respective Returns i.e. Excise return and Service Tax return ???