Returns the characters from the middle of a text string, given a starting position and length.
| Name | Type | Description |
| arg1 | string | The text string from which to extract the characters. |
| arg2 | number | The position of the first character to extract. The first text character is 1. |
| arg3 | number | A number of the characters to extract. |
builder.CreateFile("xlsx");
var oWorksheet = Api.GetActiveSheet();
var oFunction = Api.GetWorksheetFunction();
oWorksheet.GetRange("A1").SetValue(oFunction.MID("Online Office", 3, 4));
builder.SaveFile("xlsx", "MID.xlsx");
builder.CloseFile();