We've created a form called frmAccounts that lists all records in the Accounts table. We've then created a textbox called TotalUnits that displays the number of records in the Account_units table (for the account displayed on frmAccount).
If you view the Properties for the TotalUnits textbox, you can see that the Control Source property is set to:
=CalcUnits([AcctNo])
This textbox is linked to a custom function that we've created called CalcUnits. You can find this function defined in the Module called modGeneral in our sample database.
This function accepts the AcctNo as the parameter. It then queries the Account_units table and returns the number of records that exist for this AcctNo.
