In the formula field it is possible to use VBscript alike type of functions. There are some examples in our online manual and also in the Knowledge Base (see here) for the most commonly used functions such as Label(), In() and If(). A comprehensive list is attached below

++ Increase value of variable
-- Decrease value of variable
% Make percentage (* 0.01)
-@ Negate the value (* -1)
+@ Make value positive
^ Power
^@ Integer power
* multiply
/ division
div Integer division
mod modulus
+ add
- substract
> Larger then comparison
>= Larger then or equal to comparison
<= Smaller then or equal to comparison
< Smaller then comparison
<> not equal to
= equal to
in is the first value in the list of other parameters e.g.: in(1, 3,4,5,6,7,8,1,2,9) returns 7, as the first value is found in the 7th position in the list of other parameters, if not found 0 is returned
not not binary operand
or or binary operand
and and binary operand
xor xor binary operand
exp the value of e raised to the power of x
if if x=True(or 1) then y else z if(true, truevalue, falsevalue)
iif if x=True(or 1) then y else z iif(true, truevalue, falsevalue)
'randg' draw from normal distrib. (mean=x, sd =y)
sqr the square of a number (x*x)
sqrt the square root of a number
abs absolute value
round round to given number of digits
trunc truncates a real number to an integer
ln natural logarithm of x
log10 logarithm base 10 of 
logN logarithm base x of y
power power: x^y
pow power: x^y
intpower power: x^y
max the maximum of both arguments
min the minimum of both arguments
sin sine of an angle in rad
cos cosine of an angle in rad
tan tangent of an angle in rad
arcsin inverse sine in rad
arccos inverse cosine in rad
arctan2 inverse tangent (x/y) in rad
arctan inverse tangent (x/y) in rad
sinh hyperbolic sine of an angle in rad
cosh hyperbolic sine of an angle in rad
tanh hyperbolic tangent of an angle in rad
arcsinh inverse sine in rad
arccosh inverse hyperbolic cosine in rad
arctanh inverse hyperbolic tangent in rad
degtorad conversion of degrees to radians
radtodeg conversion of rad to degrees
textvalue returns numeric value of text variable (e.g.: tekst value contains '3456' then that is returned as a value, if the text variable contains '3456T' system missing is returned
label Is the first parameter true return the second, third true then return 4th, Nth (oneven) is true return Nth even parameter
notmissing return the first value that is not sysmissing from the array of parameters
avg returns the average of the passed values
IsNull Equals spps null system missing
IsNotNull Not equals spps null system missing
contains Is the first parameter in the others (equals in function)
choose return the value, specified at the index given by the first parameter
in Is the first parameter in the others
date_year Get the year
date_month Get the month
date_date Get the day
date_dayofweek Get the day of the week as a number
date_week Get the week number
date_hour Get the hour
date_minute Get the minute
date_second Get the second
now Get the current date/time
pos Position in of substring in string e.g. pos('world', 'Hello world') returns 7 (position found)