This is my solution. The code fragment shows how the eval function was used to form a function call. The code checks for the existence of the js function before calling it. It also passes two string parameter values.
targetPageScript = the name of the JavaScript in the external library
parm1 = the value of the 1st string parameter
parm2 = the value of the 2nd string parameter
if (eval('typeof(' + targetPageScript + ')') == 'function')
{
eval(targetPageScript + '("' + parm1 + '", "' + parm2 + '");');
}
else
{
alert('JavaScript function "' + targetPageScript + '" could not be found. No attempt was made to call the function.');
}