Step 1: Click a button to show a box
Step 2: User enters data into box
Step 3: User's data from box is entered to a cell on the sprdsht
Step 4: Another macro processes the information in that cell

Is that correct? If yes, then this code could do it for you. Note
that some lines have an apostrophe, which is a user note (the compiler
ignores everything on the line after the apostrophe).

Sub Get_User_Input()
Dim Response

Response = InputBox("Please enter data:") 'get user input
Range("a10").Value = Response 'apply that input to a cell: change this
from a10 to your cell address
MyMacro 'call the other macro: change "MyMacro" to the actual name of
the macro that should run
End Sub