Here's one that I built up the other day for another posting:

=IF(LEN(A1)<7,"",IF(VALUE(MID(A1,2,1))2,"0"&A1,I F(LEFT(A1,2)="10",LEFT(A1,2)&"0"&RIGHT(A1,5),IF(VA LUE(LEFT(A1,1))1,"0"&A1,"check"))))

You can see that there are 4 IF functions and quite a few string
functions, and this is one which I actually built by adding text
representations of the actual formulae, plus a bit of manual adjustment
to the composite strings. Works for me in cases like this.

Pete