field selection in me54n

Hello Experts,

we are using different documents types like

Domestic PR,

Project PR,

Import PR,

Service PR,

when the PR has to be released it has to be released. the first releaser has to check the cost center and G/L account.

if they are wrong than the releaser has to change the cost center and G/L account.

my problem is the fields cost center and g/l are in editable mode in all document types except for service PR.

can any one help me out in this.

thanks,

murali