InfoPath Dev

Hello Everyone,
New to Infopath and using infopath 2007. I would like to know how to do the following:
I have a drop down box that lists a bunch of things. I have a field in the datasource and when the field has a value in it i want to filter the contents of the drop down box from the value in the textbox. The contents of the drop down box come from the database via a seconday datasource and it is filled when the form is opened. So when the text changes on the field i want to re-query the drop down box so that the contents of the drop down are based on this field... does anyone know how to do this???
Thanks,

Use a query data source rule on the text box.

Hi Greg,
Thanks for the reply. This is a good step however I just can't figure out how to inject a value from my info path form into the query. Can you provide steps to do this in info path 2007?
Thanks,
Erin

Ok i've figured this out.. here's how i've done this in infopath 2007.

if ( e.NewValue != "" )
{
DataConnection objADOAdapter;
AdoQueryConnection connection;

objADOAdapter = this.DataSources["NavigationGroups"].QueryConnection;
connection = ( (AdoQueryConnection)( objADOAdapter ) );

// Retrieve the field in the InfoPath form whose value will be used in the WHERE clause
XPathNavigator node = this.CreateNavigator().SelectSingleNode( "/my:myFields/my:group10/my:cbIdentifyAssetFilterTypes",this.NamespaceManager );

if(connection.Command.Contains("inner join"))
{
//i want to remove the inner join text if there is already an inner //join so that i can append the new join condition.
int index = connection.Command.IndexOf( "inner" );
connection.Command = connection.Command.Remove(index );
}
// Generate the new SQL statement with the INNER JOIN and WHERE clause
string strSQL = connection.Command + " inner join linker_parent_to_child_nav l on l.childid = NavigationGroups.id where parentid = '" + node.InnerXml + "'";

connection.Command = strSQL;

this.DataConnections["NavigationGroups"].Execute( );

}

Looks good. Glad you got it working!