onBeforeFileUpload

fires before file uploading has started

void onBeforeFileUpload(string mode,object loader, [object formData] );

mode	string	the mode in which uploader is used (read more about uploader modes here)
loader	object	XMLHttpRequest object related to the data loading
formData	object	optional, form config

myVault.attachEvent("onBeforeFileUpload",function(mode,loader,formData){
    // your code here
    return true;
});

Details

This API page is for Vault v2.5. Please go to docs.dhtmlx.com/vault/ to see API reference for the current version of dhtmlxVault.

Returning false will cancel the 'upload' operation.