I want to pull records in a proc.

If both @CreditLimitMin and @CreditLimitMax were passed, then it should pull records with limits in between both
If @CreditLimitMin was passed and @CreditLimitMax was not, then it should pull records a limit equal to or above it
If @CreditLimitMax was passed and @CreditLimitMin was not, then it should pull records a limit equal to or below it


Here's what I have so far

SELECT * 
	FROM Customers
	WHERE RecordId = ISNULL(@RecordId, RecordId) AND
		  FirstName = ISNULL(@FirstName, FirstName) AND
		  LastName = ISNULL(@LastName, LastName) AND
		  BETWEEN @CreditLimitMin AND @CreditLimitMax AND
		  State = ISNULL(@State, State) AND
		  Active = ISNULL(@Active, Active)

What am I doing wrng here?