This function is used to apply a designer property in customization scripts. 

Parameters:

• obj – the object or element to which design property will be applied. This could also be an element ID (string)
• propName – name of the designer property to apply to the object.
• propValue – value of the designer property to apply to the object.
  

Example:

The code below changes a textbox to a date field by changing the design field type designer property into a date field rather than textbox:

var myTextBox = getObj("TextBox1");     //get the textbox object reference

applyProperty(myTextBox, "field type", "date field");