I agree with Frank that it would be better to separate each value into its own
cell.
But if you want you could use a userdefined function:
Option Explicit
Function Eval(myStr As String) As Variant
myStr = Application.Substitute(LCase(myStr), "x", "*")
Eval = Application.Evaluate(myStr)
End Function
Then use another cell with:
=eval(a1)
If you're new to macros, you may want to read David McRitchie's intro at:
http://www.mvps.org/dmcritchie/excel/getstarted.htm
Short course:
Open your workbook.
Hit alt-f11 to get to the VBE (where macros/UDF's live)
hit ctrl-R to view the project explorer
Find your workbook.
should look like: VBAProject (yourfilename.xls)
right click on the project name
Insert, then Module
You should see the code window pop up on the right hand side
Paste the code in there.
Now go back to excel.
Into a test cell and type:
=eval(a1)
This function is pretty specific. You may want to start using standard
arithmetic operators in your strings to make it somewhat more useful:
12 * 6 * 20