How to pass multiple parameters to Telerik:RadButton

Question

I have 2 telerik:RadGridView object (named FTP and Email grid) separated by pagetabs that a user can choose multiple records from by clicking a row. I need to pass those 2 telerik:RadGridView objects after the user clicks on OK as I need to know which records were selected by the user and from which grid they belong(whether EmailGrid or FTPGrid). I've read how to do multiple bindings from this link:

Passing two command parameters using a WPF binding

but I'm not sure how to add them to my code as the syntax seems different because we are using telerik.

Our code looks like this:

<telerik:RadButton Content="Select Client" 
HorizontalAlignment="Left" Margin="5" 
Command="{Binding SelectClientCommand}" 
VerticalAlignment="Top" Width="75" 
CommandParameter="{Binding SelectedItems, ElementName=gridEmail}" />  <----- This is where I want to pass my 2 grid objects 

and the suggestion from the link above seems to have a different syntax:

     <MultiBinding Converter="{StaticResource MyMultiConverter}">
         <Binding Path="..." ElementName="MyTextBox"/>
         <Binding Path="..." ElementName="MySomethingElse"/>
     </MultiBinding>

I can't seem to make it work. Any suggestions how to do this?