If you just want the static value, you don't need any code.
To set the controlsource property, highlight the textbox
Go to the properties window
In the box next to Controlsource, enter
Sheetname!F3
Substitute whatever your sheet is called for "Sheetname"
If the name of the sheet has spaces in it eg "Master Sheet"
you will need to emclose the sheet name in ' 'ie
'Master Sheet'!F3
HTH Rgds
~Geoff~