You are trying to use a separator from an "array formula"... please see the help subject in Excel. Type in "semi-colon" and you'll find the following:
A basic, single-value formula produces a single result from one or more arguments or values; you can enter either a reference to a cell that contains a value or the value itself. In an array formula, where you might usually use a reference to a range of cells, you can instead type the array of values contained within the cells. The array of values you type is called an array constant and generally is used when you do not want to enter each value into a separate cell on the worksheet. To create an array constant, you must do the following:
Enter the values directly into the formula, enclosed in braces ( { } )
Separate values in different columns with commas (,)
Separate values in different rows with semicolons (;)
For example, you can enter {10,20,30,40} in an array formula instead of entering 10, 20, 30, 40 in four cells in one row. This array constant is known as a 1-by-4 array and is equivalent to a 1-row-by-4-column reference. To represent the values 10, 20, 30, 40 in one row and 50, 60, 70, 80 in the row immediately below, you would enter a 2-by-4 array constant: {10,20,30,40;50,60,70,80}.
Hope that helps....