How can I detect all the variables or recognize their classes in any VB code?

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C#

VB

Hello to everyone
I have to implement Chapin metric functionality(via C#) (complexity of programs). The metric should detect all variables of a VB code and somehow determine their corresponding classes:
P = number of input variables (including global variables) that are used in calculating the output
M = number of variables that are modified or created in the method
C = number of variables that participate in determining control flow
T = number of variables that are unused But these traditional software complexity metrics are applicable at the method level.
How can this thing be done? As I realize regular expressions is not the best way. Maybe there are some lexical parsers/analyzers of vb code?

Any help is appreciated!