When executing a method using OP Execute On Server the variable names must be passed as parameters, rather than passing the values. For example if you want to execute a method named "Addition" with the arguments being 1 and 1 you would have to call the OP Execute On Server command like this:

$param1:=1
$param2:=1
$error:=OP Execute On Server($connectID;"Addition";1024*64;$processID;"$param1";"$param2")

The documentation for the command can be found online:

https://www.4d.com/4ddoc2004/CMU/CMU10753.HTM