Combine Expressions in ExecIf command

How do I combine several expressions into a dial plan with ExecIf command?

So, several conditions have to be met for the application to be executed.

What I have is:
exten => s,1,ExecIf($["${AMPUSER}"=“8700”]?System(echo…

So I would need something like ExecIf($["${AMPUSER}"=“8700”] + another condition, e.g. “Ext ${AMPUSER}”=“1000”

How is that done and how does a “Either or” expression look like?

Thanks.

https://wiki.asterisk.org/wiki/display/AST/Operators