I sincerely appreciate whoever's help on this question!

I need to use Excel formula functions of COUNTIF and SUM in VBA. The range
for calculation need to refer to a variable set in the VBA which is changing
from one worksheet to another. However, the variable can't be recognized by
the COUNTIF function. The actual statement is:

Selection.Value = "=COUNTIF(RC[1 - C]:RC[- 1], ""Abs"")"
or
Activecell.FormulaR1C1 = "=COUNTIF(RC[1 - C]:RC[- 1], ""Abs"")"

This formula is to count the number of "Abs" within the left (C-1) columns
of the activecell. "C" is the variable set in VBA that has to be used for
iteration steps in diferrent worksheet. Activecell is changing within 1
column of individual worksheet.
Must be writen into VBA because number of activecells is uncertain when
design.

How to make Excel function work by using the variable "C"?