Range.AutoFill (Excel)

Performs an autofill on the cells in the specified range.

AutoFill (Destination, Type)

Set sourceRange = Worksheets("Sheet1").Range("A1:A2") 
Set fillRange = Worksheets("Sheet1").Range("A1:A20") 
sourceRange.AutoFill Destination:=fillRange

Arguments

The following argument is required

Destination (Range) - The cells to be filled. The destination must include the source range.

The following argument is optional

Type (XlAutoFillType) - Specifies the fill type.

Here you can find possible values for XlAutoFillType.