Use VBA to create and insert an indirect relative formula

[cdratz]

I imagine it is, but I can't seem to get it quite to work. I'm two days into youtube videos and forum hunting and could use some help!

I think I'm close with object variables as a range but I can't seem to get the formula to use the formula contained in another cell, much less offset a given amount from that range. I tried it as a string, but then I couldn't use offsets.

I want to:

1st) define a variable as a range (a single cell) referenced in formula(not the value) in another cell
2nd) use that range with offsets to make a FormulaR1C1 formula.

Sub Choose1()

   Dim Fir As Range
         
    Set Fir = ActiveCell
    
           
    ActiveCell.Offset(0, 1).Select
    ActiveCell.FormulaR1C1 = "=SUM(fir.offset(0,1),fir.offset(10,1),fir.offset(20,1)"

End Sub

Say Cell A1{activecell} = A3

And I want the Formula in B1{always activecell.offset(0,1)} to = Sum(B3{always the same row number as the formula in A1, and offset 1 column to the right},B13{always activecell.offset(10,1)},B23{always activecell.offset(20.1)})

Please help!