You can execute VBScript from within the script execution in one of two ways.
1. Use the script EXECUTE statement.
EXECUTE cscript c:\dir\sendmail.vbs parms
not sure I got the syntax exactly right, you'll have to experiment.
2. Functions that are included in the qvw module (Ctrl-m) can be called as script functions from within the script. For example, if you coded a function named sendmail that took a single parameter in the module.
LET x = sendmail(toaddr);
LOAD sendmail(toaddr) as X, ...;
For an example of creating and calling a script function, see: