External
Purpose 
Accesses plug-ins created for versions of FileMaker Pro prior to 7.0 and uses the syntax External(“function name”, parameter), where function name is in quotes and is the name of an external function.
Format 
External(nameOfFunction;parameter)
Parameters 
nameOfFunction - the name of the external function
parameter - the parameter(s) required by the external function. A parameter is required, even if it’s only 0.
Data type returned 
Depends on the external function
Originated in 
FileMaker Pro 6.0 or earlier
Description 
Plug-ins created for FileMaker Pro version 7.0 and later do not use the External(“function name”, parameter) syntax. For more information, see External functions.
Related topics 
Functions reference (category list)
Functions reference (alphabetical list)
About formulas
About functions
Defining calculation fields
Using operators in formulas