Echoing what Pfeil is talking about, {PROCESSEXISTS:} cannot accept explicit text (like "~~Steam" in your example). This token takes a text variable as input. So you must first define a text variable with a value of "~~Steam" and then you can insert that text variable as {PROCESSEXISTS:YourTextVariable} for evaluation.
The below example allows you to specify the process (EXE) name (here I'm using the calculator) and "business time" range of interest, and the command will check these against existing processes and the current time.
// Define process of interest in text variable
Set Text [~~MyProcess] to 'calculator'
// Define range of times of interest. Only the time matters here.
Set date [~~BusinessTimeStart] value to 10/23/2018 5:00:00 PM
Set date [~~BusinessTimeEnd] value to 10/23/2018 10:30:00 PM
// Check if current time is within time range of interest
Begin Condition : ([{EXP: IIF({TIMEHOUR24}+{TIMEMINUTE}/60>={TIMEHOUR24:~~BusinessTimeStart}+{TIMEMINUTE:~~BusinessTimeStart}/60, 1, 0)}] Equals '1' AND [{EXP: IIF({TIMEHOUR24}+{TIMEMINUTE}/60<={TIMEHOUR24:~~BusinessTimeEnd}+{TIMEMINUTE:~~BusinessTimeEnd}/60, 1, 0)}] Equals '1')
// Check if process of interest is running
Begin Text Compare : [{PROCESSEXISTS:~~MyProcess}] Equals '1'
// Lecture accordingly
Write [Blue] ''{TXT:~~MyProcess}' is running during business time' to log
Write [Blue] 'Naughty naughty Kool-Aid' to log
End Condition
Else
// Game on!
Write [Blue] 'Outside business hours. Have fun!' to log
End Condition
Note that the command only looks at the time portion of the date-time variables when evaluating whether you're within the "business time" window. You can insert the conditional statement block into a loop to keep evaluating the statements, though you'll want to also add a pause (maybe 5 or 15 minutes?) at the very end of the conditional block (but still within the loop) so you don't loop constantly. Depending on your needs you may also want to include a way to break out of the loop.
I haven't made a lot of commands involving date-time variables, and there may be more efficient ways of evaluating if the current time is within "business time."
HTH