Can't make work SetExportValues method

trying to assign new values to radiobutton in Vbscript, but get a mistake:

"Invalid call procedure or argument"

Can't figure out what's the problem.

Set field =Form1.Fields("Radio")

Dim arrExportVal(1)

          arrExportVal(0)="Left"

          arrExportVal(1)="Right"

   field.SetExportValues arrExportVal

Thanks