Macros Serial number generation with repeatability comparison base

[K0st4din]

Hi all, after a lot of searching I managed to find something similar on the site that comes close to what I want to do.

Macro to generate random serial number

Hi guys, I need to generate some serial number to provide to our students and I'm looking for a macro to do it. Ideally, I enter in cell A1 the number of key code to generate and it will generate those in the following format: 3XA7-BC6D-98EF Can mix letter (Capital only) and number. But should...

www.mrexcel.com

But since I don't understand anything, I can't even modify it for my needs, I am asking for your macro help.
I will attach my excel file.
I want to generate random serial numbers and in different situations with different character lengths ie 12 or 14 or 16 or 18.
In cell I2 I have made a drop down menu to choose how many characters to be. In cell J2 - what type should they be (ie Only uppercase letters and numbers, only numbers or lowercase, uppercase and numbers, or some of my choice of selected characters, etc.).
In cell K2, I record how many Countless combinations to generate according to the choices made that start from/in cell A1 to the end (just an example: be it 3, 34569 or 1 million).
Here it comes (and what I was able to find on the site) is to be able in the second worksheet (with some name given by me) to be able to accumulate a base, with already generated combinations, so that there is never repetition in the new ones generated.
Since I have no idea if the macro can add columns, I have made several of the different types of combinations, be it 12, 14, 16 or 18. If after the first column is filled, the macro can add a new column with the search criteria, then it will make no sense for me to put columns for each type (but I leave this as a last touch, to have your say).
I would be extremely grateful if you could help me.
One more thing, in the link where I found a similar solution, there the user requires to have some hyphens, in my case, I don't need them, that is, I need something like this: for example: ODN81T6DRJJY8S or ODN81T6DRJJY8S49 or 068249317896) i.e. is without any signs.
Thanks in advance to each one!

Test serial numbers.xlsm
	A	B	C	D	E	F	G	H	I	J	K	L	M	N	O	P
1									? Combination	Select model letters and numbers	How many numbers you need			12	ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789
2									14	ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789	987254			14	ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789
3														16	abcdefghijklmnopqrstuvwxyz0123456789
4														18	0123456789
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generate numbers

Cells with Data Validation
Cell	Allow	Criteria
I2	List	=$N$1:$N$5
J2	List	=$O$1:$O$11

Test serial numbers.xlsm
	A	B	C	D	E	F	G	H	I	J	K	L	M	N	O	P	Q	R	S	T	U	V	W	X	Y	Z
1	12	12	12	12	12	12	12	12	14	14	14	14	14	14	14	14	16	16	16	16	16	16	16	16
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base generated numbers

 

[StephenCrump]

If you are going beyond a few million, using a VBA dictionary is going to be increasingly slow, and the Excel workbook is going to get bloated. I'd be looking for non-Excel solutions.

The speed will depend on what the purpose of your codes is. Unique codes are easy and quick to generate if you don't need randomness. But if you want random, for strong cryptography, that will take longer.