I have problem writing formula for the below case:

I have a date time field  and 2 different single line of text fields

EndDate : Date Time (e.g: 12.05.2008)

EndHour : Single Line of text (eg: 09)

End Minute : Single Line of Text (eg: 30)

I want to create a calculated  field named

EndTime : DateTime (for the above case 12.05.2008 09:30)

I don't want EndTime to be Single Line of text to be able to sort according to
this field.

Any idea?

How can I calculate  a number field  (NumValField) into a currency US
dollars....

Sounds like you'll need a conversion factor somewhere; this might be a good
candidate for a lookup field, if you're keeping your conversion rates in
another list. Then you can just do the multiply/divide operation in your
calculated field  and choose to display as currency.

Here's what I would do:

Create a new Date/Time column in the task  list called "Completion Date".
Create a workflow in SPD to run when task items are changed, that does
the following:
If Status = Completed, set "Completion Date" to Today.

Then, as a bonus, you could use content types to hide that "completion
date" field  from forms, so that no one can edit it directly.

I thought this calculated  field was working? It appears to work with
Gate1 Rvw and from this point it will not work.

=IF([Gate1 Rvw]="","",IF([BD Status]="Qualified Gate 1",[Gate1 Rvw],IF([Gate2
Rvw]="","",IF([BD Status]="Qualified Gate 2",[Gate2 Rvw],IF([Gate3
Rvw]="","",IF([BD Status]="Qualified Gate 3",[Gate3 Rvw],IF([Gate4
Rvw]="","",IF([BD Status]="Qualified Gate 4",[Gate4 Rvw],""))))))))

I was able to get this to work:

=IF(AND([Gate1 Rvw]<"",[BD Status]="Qualified Gate 1"),[Gate1 Rvw],IF(AND([Gate2
Rvw]<"",[BD Status]="Qualified Gate 2"),[Gate2 Rvw],IF(AND([Gate3 Rvw]<"",[BD
Status]="Qualified Gate 3"),[Gate3 Rvw],IF(AND([Gate4 Rvw]<"",[BD
Status]="Qualified Gate 4"),[Gate4 Rvw],""))))