How to use Calculated field

Hello abou7akm

From menu Search,, enter Calculated fields and you will have many examples of CF
JB

Hi Abu7akm,
You need to be clear that calculated fields are not 'real' fields - they do not get stored in any tables;  they only exist while your program is running.
Calculated fields can be used to avoid data redundancy - for example, you know the price and quantity of something, you could use a calculated field to display it's value (price * quantity);  holding the value in a table is redundant.
Calculated fields can be used to display data that is variable - for example, if you know someone's birthday, you could use a calculated field to display their age;  holding their age in a table is both redundant and inaccurate (it will only be correct as at the time of saving).
Calculated fields can be used to concatenate data fields - for example, if you know someone's salutation, first name and last name, you could use a calculated field to join them together (for example, in a mail-shot);  again, holding the concatenated salution and names in a table is redundant.
Calculated fields can be used to display summary information - how many invoices per customer, the most recent invoice per customer etc etc 
Please look at the attachment that contains various examples of calculated fields.
Having said that, if you are relatively new to MVD, there is a danger that this could hinder as much as help.  It might be better if you just said what exactly it is that you need to use a calculated field for and then build up your knowledge from that point.
Derek.