Speed of update record?

I have a system that generates work order numbers. There is a form with a single record that contains the next work order number. When a new work order form is opened the following code is in the on load section.

//Get the work order number record
Next_WO_Num_Record = Next_WO_Number[Record_Name == "ABC"];
WO_Number=Next_WO_Num_Record.Next_WO_Number.toString();
//Update the work order number record
Next_WO_Num_Record.Next_WO_Number=(Next_WO_Num_Record.Next_WO_Number + 1);

If two people open a work order screen at the same time they both get the same work order number. Shouldn't the 3 statements happen in milliseconds?

Is there a way to lock the WO Number Record and unlock it when the update is written?

Herb Wexler