limitations on functionality of commands sent serially?

Hi,

I'm wondering whether certain looping commands sent serially behave differently than they would if executed within a program resident on a motor. For the moment, I'm trying to see how much I can do with no program loaded on the motor.

I've found I can send a multiple-command string such as this and get the result I expect:

MP PT=1000 VT=1000 ADT=1000 G

But if I try to get a little more fancy, such as either of the following...

MP PT=1000 VT=1000 ADT=1000 G TWAIT RPA
MP PT=1000 VT=1000 ADT=1000 G WHILE Bt LOOP RPA

...the RPA command executes immediately, rather than waiting for motion to complete.

As a further experiment, when I enter the following command string, I get the following result:

x=1 WHILE (x<10) Rx x=x+1 WAIT=2000 LOOP RPA

1
1
1
1
0

where 0 is the current motor position in this case. (What's going on to give me this result?)

Can anyone tell me if sending 'mini-program' strings like this has certain fundamental limitations I should be aware of?

Thanks much,

Dave