19BII Program ---> need help!

[Aconzio]

Dear all

in searching for a program to make my HP19Bii able to calculate Calls ans Puts (plain vanilla Black&Scholes) I came to this little program (i.e. 3 different formulas) for Warrants, Calls and Puts calculation.
Now, I get an error message by the second largest and longest formula (for Warrants and simple Calls) at the point where the expressions reads"...2+.5:.5+(1+SQRT(PI))..."
Now I do not understand the logic at all and I'm not a programmer...can anyone of you help me in interpreting why 19Bii doesn't accept the expression (while having no problem with the iteration of the same string some passages later?
Many thanks!!
Aconzio[/quote]