Is it possible to nest if() statements in the wire formula manager?

Is it possible to nest if() statements in the wire formula manager?  When I do and then try to renumber, the green process bar just keeps on processing.  I have to kill the program to get out of it.

Here is a look at the formula that I am using:

IF(SUBSTR(COR_TAG,LEN(COR_TAG)-1,1)="T","C0" + SUBSTR(COR_TAG,LEN(COR_TAG),2), IF(SUBSTR(COR_TAG,LEN(COR_TAG)-2,1)= "T","C" + SUBSTR(COR_TAG,LEN(COR_TAG)-1,2),"D" + EQU_NO))

If it take out the second if statement it works fine but when I try to nest the second one is when I have the problem.

SolidworksElectrical