EXCHANGE command

I want to exchange a free characteristics with the one in columns. Will exchange command work when used via URL?

My URL is:

Url = Url + "&CMD_4=EXCHANGE%26DATA_PROVIDER%3DDP_1%26IOBJNM_1%3D"+ currentDrilldownOther + "%26IOBJNM_2%3D" + formObj.Drilldown.value;      

where currentDrilldownOther is one in columns and formObj.Drilldown.value is new free characteristic.

But its not exchanging the characteristics. whats wrong?

Abhijeet