Web Forms :: Restrict Dynamic Textbox To Set Of Values Only?

I have generated dynamic text boxes for each table row there are 6 text boxes

1. For the first two text boxes the values given by the user should be in valid range(this range comes from the database).User is allowed to enter the value within that specified values only. How to achieve this? I have taken drop down lists but if the values in drop down increases selecting required value is tedious to the user.. (if it is having 1000 values) and while I am retrieving the values I have written query such as Null values ignored. But I am getting NULL values in the dropdown here is the code what I have written,

(Database is Oracle)
If
Not (OledbCmd.Equals(String.Empty)
Or OledbCmd
Is
Nothing)
Then
OledbDA.SelectCommand = OledbCmd
OledbDA.Fill(ds, "textDB")
dt = ds.Tables("testDb") If
(dt.Rows.Count > 0) Then
ddlist.DataSource = dt If UCase(s) =
"NUMBER"
Then
ddlist.DataValueField = "num"
ElseIf UCase(s) =
"NAME"
Then
ddlist.DataValueField ="name"
End If
ddlist.DataBind()
ddlist.Items.Insert(0,
"Select")
ddlist.SelectedIndex = 0 Else
ddlist.Items.Insert(0,"Norecords")
End If
End
If

2. In the rows generated when user presses functional key F3 then the values of the above row(previous row) have to be copied in present row. similarly for F4 column copying. This I achieved through the Java script. But I have many forms requirement is same. where as text boxes id differ. how can I generalize the One function to work for all forms. I wrote as like this.

document.getElementById("No"+ cnt).value = document.getElementById("No" + (cnt-1)).value;
document.getElementById("Name"+cnt).value = document.getElementById("Name" + (cnt-1)).value;

For all the 6 text boxes.where as for column copying I wrote as

document.getElementById(id + cnt).value = document.getElementById(id + (cnt-1)).value;

here id is the text box id Which I am passing.