Making a constant and a variable in excel 2007

Hello!

I would like some help with a very easy thing in excel 2007, i guess itīs easy. Well, assume we have constant P = 100, K=50 and F=10.

I would like to "lock" these cells, and have a variable which could adjust and this variable would multiplicate each one and put out the number.

For example:

P = 100
K = 50
F = 10

Variable: 10 this would generate a sum of:

P = 1000
K = 50
F = 10

Could anyone help me?