you can just add a button and then set the relevant text via codebehind i.e.

in the ascx

<dnn:DnnImageButton ID="cmdDeleteUserRole" runat="server" AlternateText="Delete" CausesValidation="False" CommandName="Delete" IconKey="Delete" resourcekey="cmdDelete" Visible='<%# DeleteButtonVisible(Convert.ToInt32( "UserID")), Convert.ToInt32( "RoleID"))) %>' OnClick="cmdDeleteUserRole_click">

</dnn:DnnImageButton>

in the ascx.cs

ClientAPI.AddButtonConfirm(cmdDeleteUserRole, String.Format(Localization.GetString("DeleteRoleFromUser.Text", LocalResourceFile), role.FullName, role.RoleName));