addPreExecFcn
Add callback function to execute before each input data file executes
Syntax
cgvObj.addPreExecFcn(CallbackFcn)
Description
cgvObj.addPreExecFcn(CallbackFcn)cgvObjcgvObj is a handle to a cgv.CGV object. run calls CallbackFcn
            before executing each input data file in cgvObj. The callback
            function signature
                is:
CallbackFcn(cgvObj, inputIndex)
inputIndex
            is a unique numeric identifier associated with input data in
                cgvObj.Examples
The callback function, PreExecutionFcn,
is added to cgv.CGV object, cgvObj
cgvObj.addPreExecFcn(@PreExecutionFcn);
PreExecutionFcn is
defined as:function PreExecutionFcn(cgvObj, inputIndex) ... end