Sure, eg. replace
range("F3:F6") with
range(cells(3,6),cells(6,6))
or somewhere in the macro  do something along these lines:
myrange = range(cells(3,6),cells(6,6))
and use
myrange
in place of
range("F3:F6")
in the linest formula.

You could also put variables there in place of the (row,column) spec.

something like

dim rlRange as range
dim ilRow1 as integer
dim ilCol1 as integer
dim ilRow2 as integer
dim ilCol2 as integer

rlRange = Range(Cells(ilRow1,ilCol1),Cells(ilRow2,ilCol2))

Let me add 2 more hints...

1) If you have a table with variable  length, and/or width, you can use:
FirstRow = ActiveSheet.UsedRange.Row
FirstCol = ActiveSheet.UsedRange.Column
LastRow = FirstRow + ActiveSheet.UsedRange.Rows.Count - 1
LastCol = FirstCol + ActiveSheet.UsedRange.Columns.Count - 1

LastRow and LastCol sounds complicated, but makes perfect sense in case your
table does NOT start in row "1" and/or column "A". Then it is adjusting the row
and/or column number. You can use this in Pascal's range  very easily, for
example:
myrange = range(cells(FirstRow,6),cells(LastRow,6))

2) If you know the first row and column, you can use:
Range(Cells(2, 2), Cells(2, 4).End(xlDown)).Select
which will select row 3 till the end of your table for columns B, C and D