I believe i have figured it out (or at least a way): calling mmBindingStrategyDataGrid.RegisterBoundControl with a reference to the grid. (see below)

[
Category("Search Criteria"),
Description("Binding source of the grid."),
Browsable(true),
DefaultValue("")
]
public virtual string BindingSource
{
get { return _BindingSource; }
set
{
_BindingSource = value;
this.grdItems.BindingSource=value;
mmBindingStrategyDataGrid.RegisterBoundControl(this.grdItems); <== new line
}
}
private string _BindingSource = "";