Setting a Firemonkey control OnMouseMove method

I have a custom control for which I am trying to define an OnMouseMoveFunction. Essentially, the control functions as a search bar, and is made up of an edit box with a child custom TGrid control for displaying results. I am handling several mouse events for the TGrid already, however when trying to implement OnMouseMove I am getting the following error when I try to set the TGrid OnMouseMove method:

E2034 Cannot convert 'void (_fastcall * (_closure )(TMouseMoveEvent))(TMouseMoveEvent)' to 'TMouseMoveEvent'

Here is the piece of the header file where the function is defined:

void __fastcall GridMouseMove( TMouseMoveEvent * MouseEvent );

Here is the actual function inside the control's CPP file:

void __fastcall TFmSearchBar::GridMouseMove( TMouseMoveEvent * MouseEvent )
{
    //handle event here
}

Up to this point everything will compile just fine. However, when I go to assign the TGrid's OnMouseMoveEvent handler to the method I have assigned, I get the error.

void __fastcall TFmSearchBar::SetGridProperties()
{
    FGrid->OnKeyDown  = GridKeyDown;
    FGrid->OnClick = GridClick;
    FGrid->OnMouseEnter = GridMouseEnter;
    FGrid->OnMouseLeave = GridMouseLeave;
    FGrid->OnMouseMove = GridMouseMove; //This line causes the error
}

What am I missing that is causing this not to build?

Try to use declarations, generated by IDE for TGrid.

Header:

void __fastcall GridMouseMove(TObject *Sender, TShiftState Shift, float X, float Y);

Implementation from cpp:

void __fastcall TFmSearchBar::GridMouseMove(TObject *Sender, TShiftState Shift, float X,
          float Y)
{
    ShowMessage("123");
}

Assignment (the same):

void __fastcall TFmSearchBar::SetGridProperties()
{
    ...
    FGrid->OnMouseMove = GridMouseMove; //This line causes the error
}