if statement help!

Let me start with this: Do yourself a favor and learn how JavaScript works. You cannot copy and paste your way to a successful solution if you don't know what you are doing. You need to be able to adapt what you find here to your specific requirements, and fix potential problems when the requirements change in the future. Here is some information about how to learn to program in JavaScript for Acrobat: Learning to Program JavaScript for Adobe Acrobat - KHKonsulting LLC

What you want to do is test one field for content, and then set a second field to some information. This is normally done with a custom calculation script in the second field. Let's say you have a field named "Dropdown", to get it's value and test if it's not empty, you would use something like this:

if (this.getField("Dropdown").value != "") {
  event.value = "some information";
}

To get the current date in the format "dd/mm/yyyy" into the field, you can change line #2 to this:

event.value = util.printd("mm/dd/yyyy", new Date());

Depending on how you set up your dropdown list, this may still not work: Via the user interface, you cannot create a truly blank entry. You would have to use e.g. one space. If that is what you did, you need to adjust line #1 in the code above to test for "unequal to one space":

if (this.getField("Dropdown").value != " ") {