Get values based on Dropdown box selection-Important

Question

Hi All,
In first table, i have an two textfields one is for "item no" and other is "item desc" and in the second table I have an "dropdown box" and "item desc".
Whatever is entered in the "item no" its populating in the "dropdown box", when an dropdown is selected any item that item desc should be displayed.
For example: In first table
Item no  Item Desc
item 1   abc
item 2   def
item 3   ghi
and in the second table
Dropdown box   Item desc
item 2   def
item 3   ghi
When am selecting item2 in dropdown box the related text is not getting dispalyed. And moreover the using instindex and the value is populating 0, below is the script
var Instindex = xfa.resolveNode("Page1.Subform1.Table1.Row2.Calculation").rawValue;
app.alert(Instindex);
var my_concatcomm = xfa.resolveNode("Page1.Itemtable.Table2.Row2[" + Instindex + "].EnterItemDescription").rawValue
var my_concatcomm = "Page1.Itemtable.Table2.Row2["+ 3 +"].EnterItemDescription"
app.alert("Index value::"+ xfa.resolveNode(my_concatcomm).rawValue);
Can anybody please help me on this.
Thank you for your help in advacne

Answer 1

Yes one more thing, i do not want any buttons or anyother webitem to be clicked to get this. this should be set with some commands if avilalbe or some other guess ?