Changing cell range based on another cell's value?

[totalbs88]

how do you create a cell formula that changes its cell number depending on another cell?

example:
=Sum(J6:J(C5))

C5 = 20

I'd like it to end up being
=Sum(J6:J20)

but have the ability to change it in case I'd like to.

Or are there any other ideas that I can work around to do something along these lines?

[Harley2]

Try =Sum(J6:INDIRECT("J"&C5))

[NBVC]

or without the volatile INDIRECT function:

=SUM(J6:INDEX(J:J,C5))

[totalbs88]

yup those worked! thanks so much!