Xailer & OZ Software

Hi,
Can someone tell me what is wrong?
oDataSet:AddCalcField("Full", { |oField| oField:oDataSet:First + " " +
oField:oDataSet:Last }
// if oDataSet:first is "JONH" and oDataSet:last is "SMITH" then
oDataSet:full is "JOHN SMITH", OK.
oDataSet:Edit()
oDataSet:first := "JOE" // or oDataSet:first(dsOBJECT):varput("JOE") or any
other way that could update this field...
// the odataset:full does not change, its value continue "JONH SMITH"...
WHY????
oDataSet:update()
// now work...but I need this while the dataset is in Edit mode!!!!
:(
Any idea?