Wierd Result in Access Calculation

[chegra26]

I have a field named InvoiceNo which is a combination of 3 other fields. These fields are ActivityABB, Date, and BusNo
The purpose of the field is to create a customized invoice number based on the activity the date and the bus number. I am using the following calculation, which should result in a combination of the three fields. However, when I change the bus number, the field sums this with the existing bus number instead of just changing the bus number.
Any suggestions?
InvoiceNo: [ActivityABB] & [Date] & "-" & [BusNo]

Thank you

 

[xenou]

Hi,
What are the data types of the fields?
Can you provide a little sample data to show an example?

 

[chegra26]

The fields are all populated from other tables as a look up.
ActivityABB is text
Date is a medium date field
BusNo is short text in the main table named Busses, However the BusNo field changes to a number when I use it for a lookup, which I am assuming why the invoice number doesn't populate correct.
The Invoice number should look like FL03082016-51. FL is the Activity ABB, 03082016 is the date, I added the "-" and 51 is the bus number. However if I change the bus number, the invoice number changes and the last number is not the bus number itself. It seems like it calculates the previous number with whatever I am changing it to. Don't know if this makes sense.

 

[xenou]

If everything is based on lookups then you probably need to look at your lookups as a potential source of the problem. Is this "combined" field actually in a table? Are the lookups actually in a table? I would suggest you don't do either - no combined fields in tables and no lookups in tables. You can keep the data in separate fields and just use the three fields as your primary key (if that's what you need). Save the concatenation for forms and reports (as needed).