dcount issues

I have been trying to get this to work for a while now

I need to perform a dcount on a table with details entered into a form.

For example its a car parking database which I need to identify if a vehicle is reofending the it need to be infringed

I am trying to perform it on a dcount so that if the vehcile has been warned a number of time then a message box with warn the user.

So i need the dcount to take into account the information within the form.

I have the following in the control source of a unbound text box with performs a count the first part works with the table colum and table name but cannot get the rest to work

=DCount("VIN","Parking Violations tbl","vin = " & me.vin.Value)

Any Ideas ?