Electrostatic field

| As you know there is an electrical field around each electrostatic | charge. I know how to create an electrostatic field. But I have problem | by creating a "variable electrostatic field". Can you give me a guide?

Electrostatic fields vary by distances from charge. That's already part of it, so you more likely are asking for a field that varies in time? In that case, you have to vary the voltage.