Changing RingDial label at runtime

Dear Madam/Sir,

 I would like to change the labels of a ringdial control at runtime. 

I tried to use the command

ReplaceListItem (panel, TOF_RINGDIAL_MUX1, 0, "2Dx", 0);

to replace the old label at the item 0 with the new one ("2Dx"). The command:

GetLabelFromIndex (panel, TOF_RINGDIAL_MUX1, 0, zp);

shows that the label has successfully changed (zp="2Dx") but the appearance of the command when the .uir is loaded at runtime is as before the label change. Is there some command required to update the appearance?

Thanks

Regards

Luca