Allows a value in non-repeatingField to be used with every repetition in a repeating field.
non-repeatingField - any non-repeating field (a field defined to contain only one value), or an expression that returns a reference to one
Data type returned 
text, number, date, time, timestamp, container
Originated in 
FileMaker Pro 6.0 or earlier
Use the Extend function with calculations involving both repeating and non-repeating fields. Without the Extend function, the value in non-repeatingField is used only with the first repetition in the repeating field.
Extend(TaxRate) * Quantity * ItemPrice returns 1.197, .6606, and 1.497 when TaxRate contains .06; the repeating field Quantity contains 1, 3, and 5; and the repeating field ItemPrice contains 19.95, 3.67, and 4.99.
Item Count * Extend(if(Company Size > 100; Reduced Price; Price)) returns $1250, $500, and $750 when Reduced Price contains $50; the repeating field Item Count contains 25, 10, and 15; and Company Size is greater than 100. If Company Size is less than 100 and Price contains $100, this calculation returns $2500, $1000, and $1500.
Related topics 
Functions reference (category list)
Functions reference (alphabetical list)
About formulas
About functions
Defining calculation fields
Using operators in formulas