Fields from a database can also be used in calculations. The prerequisite for this is that you have assigned a database to the document via the ribbon command Mailings | Select database | Use existing database.
You do not even have to enter the field names manually. If you look at the dialog box of the ribbon command Mailings | Field 
| Calculation, you will notice that the names of all database fields appear in the list Variable/field as soon as you assign a database to the document. They can be entered in the formula via a double-click.
As an example, we want to create an invoice form that can be easily printed as a mail merge. All you need is a database that contains fields for customers' personal data (name, street, city, etc.). In addition, the database should contain a QUANTITY field with the order quantity, an ITEM field with the item name and a PRICE field with the unit price. Proceed as follows:
| 1. | Use the command File | New  to create a new document. |
| 2. | With the ribbon command Mailings | Select database | Use existing database  , you assign a suitable database to this document (example: see below). |
| 3. | Next, create a normal mail merge, as described in Database. Insert the database fields with the customer data (address, etc.) at the appropriate places in the letterhead. |
| 4. | Design the invoice itself according to your needs. Enter fields from your database with the ribbon command Mailings | Merge field – for example, the QUANTITY field for the quantity ordered. |
| 5. | We now come to the highlight: You can calculate with the database fields. For example, the formula "QUANTITY*PRICE" calculates the sum for the current record. Thus, use the ribbon command Mailings | Field | Calculation to insert suitable calculations in the desired places. |
| 6. | If everything has been entered, you can save the document. If necessary, select the desired records in the database and print your invoices using the ribbon command File | Print merge. |
Example
You will find an application example in the folder with the sample documents for SoftMaker Office: the Invoice.tmdx file with its associated Invoice.sqlite database.
Depending on the operating system, you will find these files as follows:
▪Windows: In the SoftMaker\Samples folder in your Documents folder
▪macOS: In the SoftMaker/Examples folder in your Documents folder
▪Linux: In the SoftMaker/Samples folder in your Home folder
▪Android: In the SoftMaker/Samples folder on your SD card
▪iOS: In the SoftMaker/Samples folder in your App folder
Tip: After opening Invoice.tmdx, enable the option Display field names on the "View" tab in the dialog box of the ribbon command File | Properties.
Alternatively: Use the ribbon command Mailings | group Fields | Field names or simply Alt+F9
You can now see all the formulas in plain text and can understand more fully how this self-calculating mail merge works.