If you ensure that all cells of the worksheet , except cell A1 , are locked , and that the worksheet is protected , then the cursor will not move from cell A1. Is this what you want ?
If worksheet is protected you can do as suggested by NARAYANK991 and nazmul_muneer, which would be my first attempt; if it isn't then shrivallabha's method'd be required. This last one works regardless the protection status.