Callgroup, queue, what to do for solving this?

Hello i want my asterisk to make calls automatically by .call files, i have 8 output channels (SIP), when i put a .call i don’t know how to do for that this call choose a sip channel which isn’t in use, i thought something like this:
create a group of channels(ex:group_1), so instead of putting SIP/100 in the .call, i woul’d like to put group_1, when the 8 channels are busy the next call is hanged up

Any suggestions?

Thanks in advance