WebCombo has ClearSelection() and ClearSelectedValueItem() method. The explanation is as follow:

ClearSelection()
Description: Instructs WebCombo to clear any currently selected item.
Sample:

function CustomFunction(){
    // Obtain WebCombo object
    var combo = ISGetObject("WebCombo1");
    // Instructs WebCombo to clear any currently selected item
    combo.ClearSelection();
    return true;
}

ClearSelectedValueItem()
Description: Clear any currently selected ValueItem.
Sample:

function CustomFunction()
{
    var combo = ISGetObject("WebCombo1");
    combo.ClearSelectedValueItem();
    return true;
}

You can try to invoke those method in OnShowDropDown client-side event of WebCombo. It is the client-side event which specifies the client side (JavaScript) function that will be invoked when the ResultBox is about to show.

Hope this help.

hi Yudi

thanks for ur replay

i am using below code now solved

LostFocus

var combo = ISGetObject("WebCombo1");
combo.ClearResultBox();
return true;

Glad to hear that invoking ClearResultBox() method resolves the problem.

Should you need further assistance or run into any problems regarding our controls, feel free to post it into our forum. We would be happy to assist you again.

Please kindly check my response on the "type webcobo accepted duplicate value" thread in here.