What is your question exactly? Do you want to check the condition and if its true, first execute command1 and only start executing command2 after command1 has finished? Then your formula is right. The ; between formula's indicates that the first command has to be finished before the second command starts. Thus it would be:
If(condition,command1;command2,command3)
If you want command 1 and 2 to be done simultaneously to have everything finished earlier it would be:
If(condition,Concurrent(command1,command2),command3)
