This is an advanced topic intended for programmers.

Stonefield Query can use "custom" functions in various places, such as report fields. A custom function is code that does something when it's called. Custom functions allow you to do just about anything you wish, including:

• Create complex formulas and display the results in a report.

• Ask the user for a value and use that value in the report.

There are a couple of ways you can create custom functions:

• Create a text file called RepProcs.prg in the directory where Stonefield Query's data files are stored. Edit this file using any text editor (not a word processor, such as Microsoft Word, which stores binary files, but an editor such as Notepad that stores text files). This file can contain as many functions as you wish. Each function should start with "FUNCTION" followed by the function name and any parameters (in parentheses), and end with "RETURN" or "RETURN variable or expression."

• Create a text file called FunctionName.PRG in the Functions subdirectory of the folder where Stonefield Query's data files are stored, where FunctionName is the name of the function. Edit this file using any text editor such as Notepad. Unlike RepProcs.prg, this file can only contain a single function and should not include a "FUNCTION" statement. It can, however, include an LPARAMETERS statement if it accepts any parameters and should end with "RETURN" or "RETURN variable or expression."

Here's an example of a function contained in a file named CalculateCommission.PRG. This function determines the commission for a sale based on a complex formula: if the sale amount is over $1,000, the commission is 12%; between $500 and $1,000, it's 10%; between $100 and $500, it's 8%; and there's no commission for sales less than $100.

lparameters SaleAmount
do case
  case SaleAmount >= 1000
    Commission = SaleAmount * 0.12
  case SaleAmount >= 500 and SaleAmount < 1000
    Commission = SaleAmount * 0.10
  case SaleAmount >= 100 and SaleAmount < 500
    Commission = SaleAmount * 0.08
  otherwise
    Commission = 0
endcase
return Commission

To use this function in a commission report, create a new report and add the desired fields, including the sale amount field. Click the Formula button in Step 2 to display the Formula Editor. Type a name for the formula, such as "Commission Amount," and enter the following for the formula's expression:

CalculateCommission(SALESHIST.DURATION)

(SALESHIST.DURATION is the name of the field in this example that contains the sale amount.)

Turn on the Show 1000 separator and Display $ settings, and set Decimals to 2. Click OK to close the Formula Editor. The formula appears in the Available Fields list. Add it to the Selected list. When you run the report, it shows the commission calculation for each sale.