I have an Excel worksheet on a web page (using the OBJECT tag). I can
use VBscript to automate data loading into the sheet. I want to
specify that a cell (or range of cells) can only accept values from a
defined list of values (i.e. standard list validation, displaying as a
drop-down list box). How can I specify my list validation for specific
cells using VBScript?
Is it possible to define the list so that the list box displays text
values but stores corresponding numeric key values (as you can do for
a HTML select tag)?

For a cell in Excel, you can set the validation rules thru the Menu
option Data->validation. Here is the vb macro.

    With Selection.Validation
        .Delete
        .Add Type:=xlValidateList, AlertStyle:=xlValidAlertStop,
Operator:= _
        xlBetween, Formula1:="1,2,3"
        .IgnoreBlank = True
        .InCellDropdown = True
        .InputTitle = ""
        .ErrorTitle = "Error"
        .InputMessage = ""
        .ErrorMessage = "Only Numeric values can be entered"
        .ShowInput = True
        .ShowError = True
    End With