Please ,can anybody help.
yes, you can assign the OU wise approval group in Multi Org environment.
means you have to navigate to specific OU resp. to define the approval limit for that OU.
For example :
You have defined the PO approval limit of Rs.10,000 for OU1 .
For Same position, you can define the PO approval limit of Rs.50,000 for OU2 by switching the resp. to OU2.