Capture SAP Shipment information at stage level

Hi All,

We would like to capture the Shipment actual start date and end date for each stage.

to maintain this data,we have two fields in shipment at stage level (Double click on Stage - click on Duration and distance)

In this screen Start Execution and End executions fields are avaialble, whereas these two fields are greyed out.

How can we make these fields active, so as we can maintain the data in these fields.

Thanks in advance for your help.

Regards

Raju