Reg Process chains

Hi Experts

I am having -1 requirement -please help me in this

Issue : I am having 10 process chain in SAP BI  , all the process chains will run on adhoc basis by diffrent users , so when 1 user execute 1 process chains other user should not able to execute any process chain unit it completes.

I am having logic in this way.

Start--> ABAP Prog---Infopackage--DTP--DataTarger-->ABAP Prog

1.First Abap program should put a 'X'(Lock) in Tvarc table  and Last ABAP program should remove 'X' in Tvarc table.

i will maintain all the 10 process chain technical names in TVARC table ,

Please help me in logic

Thanks