popup window for input?

[shnay]

First let me say thanks for all the help this site is great! Ok now back to business...

I have a formula that works for me

=IF($D23="","",VLOOKUP($D23,Description!$A$1:$C$349,3,0))

It will lookup what I put in a cell and find the data from the other page and fill in the blank. I need one more step if excel can do it. I edited the formula to this:

=IF($D23="MAT","input amount",IF($D23="","",VLOOKUP($D23,Description!$A$1:$C$349,3,0)))

Which works except instead of the cell displaying "input amount" I would like a box to popup and prompt me for a dollar amount and then put that in the cell the formula is in but not change the formula. Can this be done?