PI Datalink with advanced PI Expression using AND Operand

Goodday,

I want to use a PI calculation by making use of PI expressions with the following PI Calculation formula.

=PIAdvCalcExpVal(IBatch!$I$20;IBatch!$C$9;IBatch!$D$9;"total";"event-weighted";"compressed";"10m";0;1;0;"PISERVER")

I have use before the following expression for IBatch!$I$20 which worked perfectly:

If (prevval('tagX') < tagval('tagX')) then (tagval('tagX') - prevval('tagX')) else 0

And now I want to incorporate the AND operator like the folowing:

IF (and(prevval('tag') < tagval('tag'));tagval('klep')= 'open') then tagval('tagX') - prevval('tagX'))) else 0

I recieve an error on this. Does anybody know why??

Is it not possible to use the AND within a IF functions in PI datalink

Regards,

Terpie