Multi-part nested IIF statement problems

[SQLHacker]

I'm converting a report from Crystal Reports to SQL Server RS 2005, and I'm stuck on a multi-part, nested IF-THEN-ELSE structure that's necessary to display the data the user wants. I don't know if I'm trying to use too many nests, or if I can't keep track of the multiple ELSE's. Below is the statement as it exists in Crystal:

IF {USER3} = "H"
THEN TOTEXT({USER3}) &
	(IF({REPEAT_FLAG} = 0) THEN "N" ELSE "P") & 
		(IF({IMPORT_FLAG} = "T") THEN "I" ELSE "") & 
			(IF(ISNULL({CUSTOMIZATION_CODE})) THEN "" 
			 ELSE {CUSTOMIZATION_CODE})
ELSE
(IF(ISNULL({USER3}))THEN ""
ELSE IF({USER3}IN ["O", "B", "W"]) 
THEN TOTEXT({USER3}) ELSE "") &
	(IF({REPEAT_FLAG} = 0) THEN "N" ELSE "P" ) & 
		(IF({IMPORT_FLAG} = "T") THEN "I" ELSE "D") & 
			(IF(ISNULL({CUSTOMIZATION_CODE})) THEN "" 
			 ELSE {CUSTOMIZATION_CODE})

If anyone can suggest the best way to deal with this (keeping in mind I know very little about C# or VB.Net) I would greatly appreciate it.