Multiply number, USING ISTIM

(a) Hey I have a function in a netlist where I want to multiply two numbers as follows:

.FUNC  u() = a*b

 But here I will not get the multiplication as asterisk will cause the rest of the line to be taken as a comment. What can I do?

(b)  For the command

I top bot STIMULUS = (V(top)-V(bot))/Resistance()

 I am getting the following error message

ERROR(ORPSIM-16346): STIMULUS <name> must be last
+ -V bot /Resistance  .FUNC

What shall I do?

I am using Orcad Cadence version 16.5 and am a newbie to Pspice.