Fill in fields from a macro

Hi, I'm a total beginner but have been trying to complete a project for work. Below is a description, any help would be appreciated.

I have a form that I want to automatically fill in from a macro searching through a range. In Range "Site" I have a drop down validation for picking the correct site. Once a value is in that field I'm looking for it to take that information and check it against another range called "SiteandRegion" then put that information into the form. Here is what I've come up with so far.

Sub auto_address()

Dim Town, County, Code As String

Let Town = WorksheetFunction.VLookup(Range("Site").Value, Range("SiteandRegion").Value, 3, False)
Let County = WorksheetFunction.VLookup(Range("Site").Value, Range("SiteandRegion").Value, 4, False)
Let Code = WorksheetFunction.VLookup(Range("Site").Value, Range("SiteandRegion").Value, 5, False)

End Sub

I think from what I've learned so far, that should collect the information? What I don't know is how to put that information into the cells. I've named the cells Town_1, County_1 and Code_1. Can anyone point me in the right direct plz.

Thx for the reply Arkadi, I put that information into my macro and it didn't seem to work. I went over it time and time again and still nothing, UNTIL, On the macro sheet itself I pressed the " Run/Sub Userform (F5) and then it entered the information. How do I get it to run automatically as soon as the site is picked from the drop down menu?

This is my code at the moment :

Sub auto_address()

On Error Resume Next

Dim Town, County, Code As String

Town = WorksheetFunction.VLookup(Range("Site").Value, Range("SiteandRegion").Value, 3, False)
County = WorksheetFunction.VLookup(Range("Site").Value, Range("SiteandRegion").Value, 4, False)
Code = WorksheetFunction.VLookup(Range("Site").Value, Range("SiteandRegion").Value, 5, False)

Range("Town_1").Value = Town
Range("County_1").Value = County
Range("Post_Code_1").Value = Code

End Sub

Thx for all your help .. I finally worked it out and it is working fine :-)