Once you use the formula =ROUNDUP(101.5,0), the cell that contains it now has a value of 102.
Just as I said for =ROUND(101.5,0), the value stored by Excel is 102
Why not put 101.5 in a different cell.
In cell A1 enter 101.5
In cell A2 enter = ROUNDUP(A1, 0)
In cell B1 enter = A1 * 2
In cell B2 enter = A2 * 2
This is what you get:
1 101.5 203.0
2 102.0 204.0
That way you still have access to the original value and you have the rounded up value as well.
If you absolutely had to extract the original value from a cell containing =ROUNDUP(101.5,0) you could write a User Defined Function - it would be specific to formulas which have a value between the first "(" and the first ","
It would not work if ROUNDUP was embedded in another formula, although you could use the same approach to extracting the value in another UDF.
The function in the cell to return the un-rounded value is =GetRU(<cell reference>)
If A1 contains =ROUNDUP(101.5,0)
and A2 contains =GetRU(A1),
then A2 contains 101.5
Here is the UDF:
Public Function GetRU(RUform As Range)
GetRU = CDbl(Mid(RUform.Formula, _
InStr(1, RUform.Formula, "(") + 1, _
InStr(1, RUform.Formula, ",") - InStr(1, RUform.Formula, "(") + 1))