Using a Variable in Excel for COUNTIF

Using a Variable in Excel for COUNTIF

First time question and I hope it's easier than I'm making this.
Can I use a variable inside a COUNTIF formula?
Currently my formula is:
=COUNTIF($C$2:$C$415,R6)
I would like to have $415 as my variable. I have tried something along the
lines of:
D1=415=COUNTIF($C$2:$C$(D1),R6) ..
but obviously get a error.
The reason I need this is column C will constantly be incrementing as I
add more rows.
Instead of going into each of my formulas and updated 415 to 416, 417 etc,
I would like to just define a Cell that can be my variable, or total rows.
Currently Column C can have blank cells, so I can't have a macro that
finds the next empty cell.. but I do however have Column A with a constant
populated cell and stops at the last ticket. However Column A is unrelated
to the COUNTIF.
UPDATE 1
I'd also like to mention that I'd be using this variable in many formulas
in the spreadsheet. Not only COUNTIF's. Also, the COUNTIF contains text.
UPDATE 2
Actually, I figured it out! I am using this formula instead:
=COUNTIF(INDIRECT("C"&D1&":A"&D2),R6)
I'm putting D1=2 and D2=415 and will just update cell D2 with how many
rows I have.
I guess I just needed to ask the question thoroughly to fully understand
what I wanted!
Thank you in advance for all help, tips and suggestions.