Help exiting function needed !!!

[Nasir.Munir]

I have written down a function which checks for "expiration" and other
like statements from another sheet within the same workbook. It
calculates that fine if I calculate that cell be cell. However, if I
calculate for the whole workbook, the calculation bar stops at 0%. When

I go into the debug mode, it takes me to the function which I wrote for

checking expiration, and then keep repeating in the same function. I
have run step by step execution, and I have found out that the control
goes back to the start even after it passes the return statement.
Someone, please help.
Here is my code:

Function DTS_Message()
sheet_name = "DTS"
count_exp = 0
count_caution = 0
' checking for negative value, if any. That shows if the value has
expired or not.
For Each cell In Sheets(sheet_name).Range("U:V")
If cell.value < 0 Then
count_exp = count_exp + 1
End If
Next cell
'if negative value found then go for expiration message.
If count_exp > 0 Then
DTS_Message = "WARNING a Discard Time Requirement(s) has
expired!"
'if not then check for other condition i.e. caution flag
Else
For Each cell In Sheets(sheet_name).Range("Z:Z")
If cell.value = "Caution flag" Then
count_caution = count_caution + 1
End If
Next cell
'if there is a caution flag found then display this
If count_caution > 0 Then
DTS_Message = "CAUTION a Discard Time Requirement(s) is
expiring shortly!"
Else
DTS_Message = "Discard Time Requirements are OK"
End If


End If


End Function