Nesting IFERROR and IF statements

I am trying to combine two different IFERROR statements with one if statement and am getting a #VALUE! error. Each of the three statements work fine by themselves, but I am having difficulty combining them into one.

The three individual statements are:
1. =IF(I2="MN-5536",30966,"")
2. =IFERROR(IF(VLOOKUP(I4,'Sheet2'!L:L,1,FALSE)=I4,""),"ENTER SUPPLIER #")
3. =IFERROR(IF(VLOOKUP(I10,'Sheet2'!$E$2:$G$65,1,FALSE)=I10,IF(S10<>"","enter supplier #")),"")

I have combined them into the below, but get a #VALUE! error.
=IF(I2="MN-5536",30966,IF(IFERROR(IF(VLOOKUP(I2,'Sheet2'!$E$2:$G$65,1,FALSE)=I2,IF(S2<>"","enter supplier #")),""),IF(IFERROR(IF(VLOOKUP(I2,'Sheet2'!L:L,1,FALSE)=I2,""),"ENTER SUPPLIER #"),"")))

Not sure if you would need to know the detail behind each function since they work fine individually. Let me know and I'll provide more detail if needed.

No I have not. I have not been able to use that successfully when there are multiple levels to a function.

It's really impossible for us to combine the 3 formulas into one without more information.
We don't know which formula is referring to which of the other formulas.

Given #1 and #2
1. =IF(I2="MN-5536",30966,"")
2. =IFERROR(IF(VLOOKUP(I4,'Sheet2'!L:L,1,FALSE)=I4,""),"ENTER SUPPLIER #")

Is #1 referring to I2 whcih contains #2?
Or is #2 referring to I4 which contains #1?

you listed 1 2 and 3.
Can you also include which cell each of the 3 formulas is in?
That way we can see how they go together.

Or better yet, post a sample workbook.

Attach a sample workbook. Make sure there is just enough data to demonstrate your need. Include a BEFORE sheet and an AFTER sheet in the workbook if needed to show the process you're trying to complete or automate. Make sure your desired results are shown, mock them up manually if necessary.

Remember to desensitize the data.

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