Novice Q: where is my combo?

I have the following JavaScript code
I do have reference to dhtmlxcombo.css and dhtmlxcombo.js

I can see all other controls (input, button) but my combobox is missing.
Any advice?

Also, how can I make a combobox to be a dropdown list, so the user is enabled to select a value, and not to type one.

THANKS!

	var formPackageData = [
			{ type: "settings", labelWidth: "120", labelAlign: "right", inputWidth: "300", position: "label-left" },

			{ type: "input", name: "form_input_1", label: "No. of pacakges", inputWidth: "50", position: "" },
			{ type: "combo", name: "form_combo_1", label: "Package type", position: "", options: [
				{ value: "form_option_1", text: "FedEx 10kg Box" },
				{ value: "form_option_2", text: "FedEx 25kg Box" },
				{ value: "form_option_3", text: "FedEx Box" },
				{ value: "form_option_4", text: "FedEx Envelope" },
				{ value: "form_option_5", text: "FedEx Pak" },
				{ value: "form_option_6", text: "FedEx Tube" },
				{ value: "form_option_7", text: "Customer Packaging" },
			]
			},
			{ type: "input", name: "form_input_2", label: "Weight (kg)", position: "" },
			{ type: "button", name: "from_continue", value: "Continue", position: "" },
		];

		var form_3 = tabbar.cells('package').attachForm(formPackageData);

SOLVED!

[*]I was missing a reference to “ext/dhtmlxform_item_combo.js”

[*]To make a combobox a dropdown list - I set the readonly property to be “1”

Yet another issue…
Once, I see my combobox - I receive an error that combo_select_dhx_web.gif is missing.
I could not find that image in dhtmlx suite, as a workaround - I duplicated one of the combo_select_dhx_*.gif images to be combo_select_dhx_web.gif

Thanks.