You have 2 problems:
1) You are confusing FOR variables with environment variables. A batch FOR variable name is always a single character, and it is access via 2 percents prior to the name: %%c. A FOR variable value cannot be changed with SET.
An environment variable name can contain multiple characters, though it can be a single character, and it is accessed by enclosing the name in percents: %var%. Exclamation points can be used if you want delayed expansion: !var!. An environment variable value is set with SET.
2) The CALL trick to access environment variable values that were set within a parenthesized code block is used at expansion time, not when you are setting the value.
I believe mousio provided provided the best answer; I always use delayed expansion like in that answer. But it is possible to do what you want without delayed expansion by properly using an environment variable and the CALL trick.
@echo off for /f "tokens=1-3 delims=," %%a in (Puck.csv) do ( echo Hello No Hockey>%%a.txt echo #:A %%a>>%%a.txt echo #:B %%b>>%%a.txt set C=%%c if /i %%c gtr 10 set C=1 call echo #:C %%C%%>>%%a.txt ) Note that it is critical that the case of the FOR variable is different than the environment variable. FOR variables are case sensitive, environment variables are not. If you use c for both, then the parser will treat %%c%% as the FOR variable followed by a percent - not what you want.