You can add property cCursorName to your grid class.

WITH ThisForm.eGridSelection && My custom Grid
  .cCursorName = SYS(2015)
  .RecordSource = "SELECT * from Customer INTO CURSOR " + .cCursorName
  .RecordSourceType = 4
ENDWITH

Yeap I know I can do it, but I would like to avoid this issue, I was thinking there is a way to know the "real" cursor linked to the grid. I need the real cursor for remanufactoring itself. If I can't do it I must add the property & remember to fill it out when I use RecordSourceType=4