HSPICE - Probing Current of an Element Defined By SUBCKT
If you want the current through a block defined by a subcircuit, then the current is defined as Ix, followed by the part's designator, a colon, and the pin as defined internally.

For example:

.subckt xxx 1 2
R1 1 2 1
.ends xxx


This subcircuit is a simple resistor, and its pins are named 1 and 2. But the symbol that uses this subcircuit can have its pins named differently. 

If they are named A and B, and if the designator is U1, then the current through pin 1 would be: Ix(U1:A).

If the pins are named similarly, 1 and 2, and the same designator, then the current would be Ix(U1:1).

If the designator would be SpecialPart13, and the pins similarly named, then the current would be Ix(SpecialPart:1).

If you look at the netlist, the block is defined as X1 ..., that is the x in Ix. If you would work with a GUI and you would see U1, most likely the netlist will show XU1 ....

So, for your case, if the netlist shows X1, and the pin is named 1, then the current through that pin would be Ix(1:1). If the name of the pin is IN, then it's Ix(1:IN).