This may help. Here is how I made a control (dropdownlist) to paste text into the FTB control based on a selection made from my dropdown. The scriptblock uses the InsertHtml function built into FTB to paste the selected value.
Dim
ftbReturn As New FreeTextBoxControls.FreeTextBox
Dim toolbar1 As New FreeTextBoxControls.Toolbar
Dim ddl1 As New FreeTextBoxControls.ToolbarDropDownList
ddl1.Items.Add(New FreeTextBoxControls.ToolbarListItem("News All", "<DIV>%%NEWS%%</DIV>"))
ddl1.Items.Add(New FreeTextBoxControls.ToolbarListItem("News Top 4", "<DIV>%%NEWS;4%%</DIV>"))
ddl1.Items.Add(New FreeTextBoxControls.ToolbarListItem("Recent Rescues", "<DIV>%%RESCUES%%</DIV>"))
ddl1.Items.Add(New FreeTextBoxControls.ToolbarListItem("Recent Rescues Last 10", "<DIV>%%RESCUES;10%%</DIV>"))
ddl1.ScriptBlock = "{ this.ftb.InsertHtml(document.getElementById(this.id).options[document.getElementById(this.id).selectedIndex].value); }"
toolbar1.Items.Add(ddl1)
ftbReturn.Toolbars.Add(toolbar1)