SharePoint - GenFireServerEvent - How can I set a fields value

I am using - {ddwrt:GenFireServerEvent(concat('__update;__workflowTaskComplete={',ddwrt:EcmaScriptEncode(string($Id)),'*',ddwrt:EcmaScriptEncode($ListName),'};__commit;__redirectsource;__redirect={_x0027__x002C_ddwrt:EcmaScriptEncode($ListName)_x002C__x0027_}'))} inside a button to complete a task, I however need to set a value of a field's name.

Can I do it in javascript or in the code above even.

Any help will be appreciated.

I think this is an XSL issue.  I don't know if it's possible though.  I'm having the same issue myself.

you can set the form field value using another javascript function and call the function in the beginning and then the genfireserverevent like..

onclick="javascript: myjavascripttosetvalue(); {ddwrt:GenFireServerEvent('__commit;__redirect={../../pagename.aspx}')}"

<script type="text/javascript" language="javascript">
 function myjavascripttosetvalue()
 {
document.getElementById(controlname).value = 'text';
}