You need to get familiar with VBA's builtin functions and use them in your code, but you're not sure where to begin.
Check out the Visual Basic Language Reference in the VBA help guide. There's a section in the language reference entitled "Functions," which includes an alphabetically organized list of builtin functions. For your convenience, I've summarized some of the more commonly used functions for scientific and engineering calculations in Table 22.
Table 22. Some useful VBA fuctions
Function 
Comment 


Returns the absolute value of the number argument. The data type returned is the same as that of the argument. 

Returns the arctangent of the number argument. The returned data type is a 

Returns the cosine of the number argument, which represents an angle in radians. The return type is a 

Returns e raised to the 

Returns the integer part of 

Returns the natural logarithm (to base e) of 

Returns 
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