after Workflow submit wants to edit quantity recieve now.

Hi,

We've started using PO workflow but when a user submits workflow and his PO gets approved, we need him to enter quantity receive in "QUANTITY TAB", "RECEIVE NOW" column for making packing slips. I'm not getting the syntax  to allow edit for purchreceivenow field only in the datasource of PurchLine. Below is my code:

 if(purchTable.State == PurchOrderWorkflowState::Approved
            ||      purchTable.State == PurchOrderWorkflowState::Completed
            ||      purchTable.State == PurchOrderWorkflowState::WorkflowCompleted)
            {
                
                purchLine_ds.allowCreate(false);
                purchLine_ds.allowEdit(false);
                purchLine_ds.allowDelete(false);
                //purchLine_ds.allowEdit(purchLine.PurchReceivedNow,true)
                I tried something like above but error.

              }

Please help.