Custom feild in task for project management

i have been working on development of project managemnent module for designing team.
i have to add customize feild name Discipline in task wich has to go through a workflow.

on submitting thetimesheet i keep on getting getting error msg :
Row #3: Discipline cannot be “MEP”. It should be one of “Design Task”

note : erp version 15

Is Discipline is Select field?

If yes, its value must be have in options.

And share more context for better answer.

Thanks @Abdeali , I was able to resolve the error. The issue was not with the Timesheet itself, but with the Link field configuration. After correcting the field configuration, it is now working fine.