I posted this once but not shwoing up after atleast an hour

I have a number in a cell I need to edit the cell by going
in and adding an = sign in front of the original number,
placing a plus just after the original number , then
entering a new number

so original cell might look like 5.734

then need to add 4.375

I need to keep both numbers so need to do calc but want to
cut down on key strokes

when done needs to read =5.734+4.375 ( a simple calc
giving me the sum of the 2 numbers in the cell

The goal is tohave a short cut key to add an = sign to the
left of a single number then jump to the right of it, add
a plus sign, and give me a blinking cursor to type in my
number I want to add to the back of it.

Thanks much

Todd