I have created a DFWP in SharePoint Designer to update a table in my
database. For some of the fields listed I would like to turn the
textbox into a dropdown and have a static list of values for the user
to choose from. Does anyone know how to edit the existing code for a
field to do this?

Here is the existing code:

<asp:TextBox runat="server" id="ff102
{$Pos}"__designer:bind="{ddwrt:DataBind('i',concat
('ff102',$Pos),'Text','TextChanged','',ddwrt:EscapeDelims(string
('')),'@USR120')}" Width="90%" />