Access Fields in Lotus Notes DB Forms

I am able to access Lotus Notes information in a form using the following.
dim Doc as Object
dim Item as Object
dim NTabN as String
Set Doc = View.GETFIRSTDOCUMENT
If Doc.HASITEM("Tab_Name") Then
Set Item = Doc.GETFIRSTITEM("Tab_Name")
NTabN = Item.Text
Else
GoTo Field_Error
End If

I am struggling trying to update this field from my excel vba program.

I have tried to use:
Function REPLACEITEMVALUE(ITEMNAME As String, NEWVALUE) but keep geting
error of object required. stumped