Parameterizing lookup field on fetchXML report to search by text not GUID

Hello, 

I am trying to parameterize a fetchXML report so that the user can enter a lookup value during runtime. I am trying to parameterize the parentsystemuserid field on the User. I am using the following peice of code to achieve this

<filter type="and">
<condition attribute="parentsystemuserid" operator="eq" value="@parentsystemuserid"/>
</filter>

When i run this report the parentsystemuserid field errors out asking for a GUID value when i type the name of the user in text. How can i change this code to filter on the text value (Name of the manager) instead of the GUID?

Thanks