Enter formula into ActiveCell

I'm using the below code to try and insert the "Value1" formula into the ActiveCell (i.e. the cell in the first blank row offset by a column, which would be in column B). Whenever I try running the code I get Run-time Error '1004': Application-defined or object-defined error for the "ActiveCell.FormulaR1C1 = Value1" line in the code. If someone could please help me figure this out that'd be great! Thank you!

Sub CreateNewVO()
'Creates the interactive dialog boxes, after inserting cells in a selected range.

Do
    Range("A3").End(xlDown).Offset(1, 1).Select
    
'A. Inserts ID number formula
    Value1 = "=IF(" & ActiveCell.Offset(0, 1) & "="""", """", MAX($B$3:" & ActiveCell & ")+1)"
    ActiveCell.FormulaR1C1 = Value1
    ActiveCell.Offset(0, 1).Range("A1").Select
End Sub