Paying time charges from your pocket

[Mark L]

Last night I went to play some 1/2NL at soaring eagle in michigan. This has a $100 max buy in (gag). After sitting down and paying your first time charge ($6 per half hour [img]/images/graemlins/frown.gif[/img] )youre already down to $94. I therefore ask if I can pay my time charge out of my pocket (I happen to have a few $1s and $5s from the casino floor on me). Dealer says I'm not allowed to do this. What is the casino's reason for this rule?