Disable focus on tabstop when TextBox is readonly

When a TextBox is in readonly and on tabbing i want to disable the focus border of the textbox, i wanted to do this in Style of textbox.Can any one help me to achieve this?

Updated the content:

Screenshot: enter image description here

Solution

Place a condition like the below in your textbox style

<MultiTrigger>
    <MultiTrigger.Conditions>
        <Condition Property="IsReadOnly" Value="True"></Condition>
        <Condition Property="IsFocused" Value="True"></Condition>               </MultiTrigger.Conditions>
    <MultiTrigger.Setters>
        <Setter Property="BorderBrush" Value="{#7B2F81}"></Setter>
    </MultiTrigger.Setters>