[NumLock]

или StrToIntDef:

StrToIntDef function
Converts a string that represents an integer (decimal or hex notation) to a number.

function StrToIntDef(const S: string; Default: Integer): Integer;

Description

StrToIntDef converts the string S, which represents an integer-type number in either decimal or hexadecimal notation, into a number. If S does not represent a valid number, StrToIntDef returns the number passed in Default.